Categorial Conflict between Phrasal-Prepositional Verbs and Infinitives: The Great Complement Shift

Abstract


Introduction
This paper focuses on the development of /to/. 'To' is commonly known as preposition, which denote direction or location; however, its function differs in context. In one context, it interacts with other linguistic elements where it precedes a noun phrase; in the other, it can interact with the linguistic elements to form structures such as, phrasal-prepositional verbs and infinitives. According to Yuliastuti (2008) , verbs are divided into single-word and multi-word verbs. The latter, which is the focus in this study, is sub-categorised into phrasal verbs, prepositional verbs and phrasal-prepositional verbs, and they are sometimes termed as verb-particles, also known as two-part words/verbs and three-part words/verbs. Mart (2012) sees the three classes of multi-word verbs as phrasal verbs whose meanings differ from the meanings of their separate parts. For instance, the meaning of the phrase look up to is different from look, up and to. In terms of meaning, Ella and Dita (2017) also note that most of the phrasal-prepositional verbs have idiomatic metaphorical meanings, which is difficult to interpret. As a result, the study adopts both Mart's (2012) and Ella and Dita's (2017) explanation in relation to meaning but departs from Mart's idea that all the divisions of the multi-https://journal.unilak.ac.id/index.php/elsya 160 Categorial Conflict between Phrasal-Prepositional Verbs and Infinitives: The Great Complement Shift word verbs are labelled as phrasal verbs. To show their difference, they constitute a verb and one or more particles (Aldukhayel 2014) as indicated in example (1) below.
(1) a. Verb + adverb (phrasal verb) go + out > go out b. Verb + preposition (prepositional verb) base + on > base on c. Verb + adverb + preposition (phrasal-prepositional verb) get + away + with > get away with A phrasal-prepositional verb, which is one of the key issues in this study, is a sub-division of multi-word verbs that constitute three words: a lexical verb complemented by an adverbial particle and a preposition (Yuliastuti, 2008;Rajković, 2017;Hussein & Fadhil, 2021). Thus, it is the combination of both a phrasal verb and a prepositional verb. The examples include come up with, make up for, do away with and look up to. Unlike the phrasal verbs that are believed to be separable, some scholars claim that the phrasal-prepositional verbs are inseparable. However, Ella and Dita (2017) argue that some structures are separable as illustrated in example (2).

The parents VP [V keep DP [D an [N axe [Adv away [P from [DP their children]]]]]].
From example (2) above, the phrasal-prepositional verb, keep away from is splitted or separated by DP an axe. On the other hand, to-infinitive is a pseudo-multi-word verb as its verb is not inflected for tense or number like the verbs in the three afore-mentioned types of the multi-word verbs. It is not a complete multiword verb because of its function in a sentence: it can function as a noun phrase, adverb and adjective, which contradicts with other multi-word verbs. However, just like the phrasal verbs and prepositional verbs, toinfinitive is a two-part word, which comprises a particle /to/ and a verb in its base form. With reference to Radford (1997) and Tjabaka (2021), an infinitive marker /to/ can be ellipted like other particles. Nevertheless, the preposition /to/, which forms part of the phrasal-prepositional verb, does not allow its complement to be ellipted.
In the last few decades ago, more attention has been given to the pitfalls of the multi-word verbs. The phenomenon has been found to be the most challenging structure, especially since it seems to be around since 2007 and still occurring in 2020. The view that it is challenging has also been supported by Rajković (2017) who affirms that the verb-particle constructions is the complex constructions. Kovács (2007) further notes that the multi-word verbs are the most challenging structures to both scholars and language learners of English. From the pedagogical point of view, Mart (2012) also states that teaching the multi-word verbs, in particular, phrasal verbs, is quite difficult. Aldukhayel (2014) also notes that there is an uncertainty that the phrasal verb structure is problematic and challenging to a number of English language learners. Preposition /to/, like other prepositions, requires a complement, which is a noun or noun phrase (NP)/determinative phrase (DP). Such complement is sometimes known as a direct object of the preposition. The NP can be in a form of a noun, pronoun or gerund, amongst others. Following the aforementioned researchers, the constructions where the phrasal-prepositional verbs are complemented by gerunds (verb +ing) seem to be problematic especially to the learners of English as L2. This is because a gerund is a mixed category, that is, it profiles like a verb and like a noun (Park 2001). As a verb, it can bear both objective/accusative and dative cases. This implies that its complements can be direct and indirect objects, respectively. Brinton (2000, p. 107) defines a case as a sign for the function of the NP in a sentence, the relationship that exists between the NP and the verb, as well as other NPs. This gerund, however, also functions as a noun.
It is, therefore, observed that due to complexity and unfamiliarity of the multi-word verb construction, the L2 students confuse such constructions with to-infinitives. Most of the time, they tend to avoid using them except for the conclusion of the application letters where they are expected to use the multi-word verbs. This is where conflict and confusion start. They sometimes complement the phrasal-prepositional verb look/looking forward to with a verb in a base form, not a gerund, assuming that /to/ always collocates with a verb in a base form. As a result, this paper seeks to describe status of both the phrasal-prepositional verb and

Literature Review
In line with literature, it has been indicated earlier that there is non-consensual terminology and classification of multi-word verb (Claridge, 2000). Quirk et al. (1985, in Blaheta & Johnson, 2001 termed them as multi-word verbs and categorised them into verb + any particle, and a particle denotes both preposition and adverb. The lack of common terminology has been reflected in McCarthy and O'Dell's (2004) study as they classified the multi-word verbs into phrasal verbs signalled by verb + particle (preposition/adverb), as well as phrasal-prepositional verbs. In trying to differentiate between a particle and preposition, DeKeyser (2000) and Dekeyser (1990) labelled the multi-word verbs as complex verbs and classified them into particle verbs, prepositional verbs and multi-word verbs. Even in 2020, there is still no consensus because Shouran (2020) has his own classification just like Mart (2012). He classified the phrasalpreposition verb as a category of phrasal verbs that is signalled by verb + adverb + preposition. In this study, the labels, multi-word verbs and complex verbs are considered synonymous, what is key is the classification of the multi-word verbs to enable the readers to appreciate the existence and difference between the prepositional verbs and phrasal/particle verbs having distinct syntactic features.
The author in this study has observed that there is a lot of literature on phrasal and prepositional verbs, but fewer studies have extensively centred on the phrasal-prepositional verbs. Basically, some scholars (Kovács (2007); Yuliastuti (2008); Mart (2012); Aldikhayel (2014); Ella & Dita (2017); Rajković (2017); Hussein & Fadhil, 2021) researched on the multi-word verb but have mainly focused on the phrasal and prepositional verbs drawing from both semantic and pedagogical perceptions. On one hand, Yuliastuti (2008) stemmed from the parallel perception. She paid attention on the characteristics of the phrasalprepositional verbs in the dictionary and compared their features with other types of multi-word verbs (phrasal verbs and prepositional verbs). The author highlighted that the phrasal-prepositional verbs are more complex than other two types of multi-word verbs. It is stated that the first particle in these verbs is the same as the one of the phrasal particel and second article is the same as the one of the prepositional verbs. Unlike the phrasal verbs, which can be intransitive (lack object), Yuliastuti revealed that the phrasal-prepositional verbs always require object complementation. This means that they are transitive. Moreover, the meanings of the phrasal-prepositional verbs are derived from the combination of their elements, but this contradicts with Marts' (2012) claim since the author viewed the phrasal-prepositional verbs as part of the phrasal verbs. In Yuliastuti's results, it has also been observed that the structure of the phrasal-prepositional verbs is a verb phrase (VP). Yuliastuti's study has extended knowledge on how the phrasal-prepositional verbs differ from other multi-word verbs. It has also taken note of the notion of structure. In spite of the given structure on the phrasal-prepositional verb, nothing has been said about the categorisation of the /to/ in the phrasalprepositional verb look forward to and to-infinitive clauses, which is key in this study.
On the one hand, the researchers such as Rajković (2017), stem from semantic perception. In her study, Rajković other than other multi-word verbs, the prepositional verbs most express notion of persuasion, and lack idiomaticity. On the other hand, scholars including Shouran (2020) and Hussein and Fadhil (2021) focused on the phrasal verbs and phrasal-prepositional phrase, respectively drawing from pedagogical point of view. Shouran's results dwelt much on the phrasal and prepositional verbs, stating that Arabic rules are different from English, which is why Libyan students make errors. His study, however, did not specifically put forth anything about the phrasal-prepositional verbs.
Contrarily, Hussein and Fadhil (2021) revealed that despite the frequent use of the phrasal-prepositional verbs in conversation, the students of the College of Education/Ibn Rushd in the Department of English seemed to be hesitant to use the phrasal-prepositional verbs in their spoken and written communication. This is because such constructions rarely exist in their Arabic languages; hence, the students found them 'tedious and fuzzy'. Even if these studies have commonality with the present paper with the notion of the multi-word verbs, specifically the phrasal-prepositional verbs, they did not articulate on the status of the phrasal-prepositional verbs and to-infinitive clauses. Little is known about the category label of /to/ in both the phrasal-prepositional verbs and infinitive clauses. In this reviewed literature, there is no comparison between the complementation of the phrasal-prepositional verbs and infinitive clauses, and all these mark the gap for the current study. https://journal.unilak.ac.id/index.php/elsya 162 Categorial Conflict between Phrasal-Prepositional Verbs and Infinitives: The Great Complement Shift For those who have drawn from syntactic point of view, such as Kovács (2007), they performed the tests to distinguish the types of multi-word verbs. It was even emphasised that the phrasal verbs and phrasalprepositional pose a problem to the learners in terms of meaning, grammatical form and style, as well as the words they collocate. Even if the collocates or complementation of the phrasal-prepositional verbs have been identified in some studies, they did not compare the complementation of /to/ in the phrasal-prepositional verbs and infinitive clauses to mark differences or similarities. Also, they did not articulate the category label of /to/ in the phrasal-prepositional verb and to-infinitives, which are the key issues in this paper.
Different from the phrasal-prepositional verbs, many scholars have had interest in the to-infinitive clauses in English. As a result, the phenomenon has been studied both diachronically and synchronically, and such scholars include (Tanaka (1997); Nakagawa (2001); Jarad (2011); Wurmbrand (2014); Gu (2020); Tjabaka (2021); Tjabaka and Morato-Maleke (2021)). These scholars have a similar view that the toinfinitive clauses in English are marked by /to/ followed by the verb in a base form. Verba (2004) emphasised that initially, the infinitives in English were verbal nouns, meaning that they possessed both the features of verbs and nouns in the Old English (OE) era. However, Tanaka (1997) and Nakagawa (2001) noted that from the OE to the Middle English (ME) periods, there was a great complementation shift of the infinitive as it is now a verbal, that is, it has lost the characteristics of nouns. In addition, the infinitive marker /to/, which initially used to assign dative case, shifted from a preposition to tense category through grammaticalisation.
From the synchronic perception, Wurmbrand (1998), Tjabaka (2021) and Tjabaka Morato-Maleke (2021) stated that infinitive clauses complement either control or raising constructions. Besides what the infinitives complement, results often seem to conflict with each other on the structure of the infinitives and categorisation of the infinitive marker /to/. This is also supported by Wurmbrand (1998) and Tjabaka and Morato-Maleke (2021) who have the same sentiments that there is no uniformity in the structure of the infinitive clauses as the structures are informed by adopted theories and concepts. For instance, Tanaka (1997), Nakagawa (2001), Tjabaka (2021) and Tjabaka and Morato-Maleke (2021) have agreement that the structure of the infinitives can be tense phrase (TP). Nonetheless, Wurmbrand (1998) has different view that the notion of restructuring and non-restructuring should be considered as not all the infinitives have the tense features. This debate raises many questions about the structure of the infinitive clauses and the categorisation of the infinitive marker /to/. This implies that this great shift has brought a lot of debate and criticism as pointed above. Even though these studies have laid a good foundation for the present study on the status of infinitives, they have only dwelt on the infinitive clauses whereas the current study focuses on both the phrasal-preposition verb and to-infinitive clause.
Generally speaking, little is known about the categorisation of /to/ in the phrasal-prepositional verb look forward to and to-infinitive clauses. Again, the status of the phrasal-verb look forward to and to-infinitive clauses and complementation of /to/ in the phrasal-prepositional verb and infinitive marker /to/ to mark their difference are seldom considered. As indicated above, this paper, therefore, seeks to describe status of both the phrasal-prepositional verb and to-infinitives. It also identifies the category label and complementation of /to/ in the phrasal-prepositional verb and infinitives marker /to/.
The study is premised within the Minimalist Program (MP). This syntactic theory is initiated by Chomsky (1995) and developed by his followers such as Boeckx and Hornstein (2010) and Krivochen and Kosta (2013), amongst others. The theory is applicable in this study because it is engaged in re-analysis of functional categories (product of grammaticalisation), which are believed to bring deeper analysis in syntax than the previous theories. According to Lindfors (2003), grammaticalisation has the following processes: desemanticisation, affixation, erosion, expansion and fossilisation. From these processes, the researcher has been able to differentiate /to/ used in the phrasal-prepositional verb and to-infinitive clauses. The theory also accounts for generation of phrases, clauses and sentences, which is through operation merge (joins two syntactic elements together to form a new syntactic unit). According to Radford (1997, p. 29) and Roberts and Roussou (2003, p. 18), all the words or lexical items in the language belong to a certain set of grammatical categories. Therefore, as the syntactic elements are merged, they are also labelled based on their grammatical categories, which has enabled the researcher to determine the category label of /to/ in both the phrasal-prepositional verb and to-infinitive constructions.
Categorial Conflict between Phrasal-Prepositional Verbs and Infinitives: The Great Complement Shift

Method
This study is qualitative in nature. Words have been used instead of numbers to have deeper insights of the status of /to/ in the phrasal-prepositional verb and to-infinitive clauses. This research approach is also relevant because it allows the researcher to undertake the study contexts out of personal interest or curiosity on issues and to access 'tacit, taken-for-granted [and] intuitive understanding of culture' (Tracy 2020, p. 7). This means that the researcher requires an explanation on how the complementation of /to/ in the phrasalprepositional verbs differs from that of the to-infinitive marker as the categorial conflict is noticed in the L2 writers' work, especially formal (application) letters. This is due to the fact that the applicants are not aware of the great shift between the complementation of phrasal-prepositional verbs and infinitive; hence, they tend to either take the complementation of the phrasal-prepositional verbs and infinitives for granted, or they have insufficient knowledge.
Based on Creswell and Creswell (2018), qualitative research allows the researcher to use multiple forms of data collection, namely, observation, field notes, interviews, focus groups, as well as analysis of documents and materials. Even though the study has been intrigued by observation from the errors of the L2 learners in concluding their application letters, the study followed unobtrusive data collection method. Babbie (2021, p. 326) defines unobtrusive method as one in which data collection method and analysis does not affect the participants of the study, meaning that it is an indirect data collection method such as content analysis. In accordance with Babbie, content analysis is all about documented human communication. As a result, the data were collected purposively and conveniently from both application and cover letters compiled by Scott (2022), where 11 phrasal-prepositional verbs and 14 infinitive clauses were identified. This is because the researcher was interested in grammatical constructions of the phrasal-prepositional verbs and to-infinitive clauses. In addition, the researcher collected the data from the internet where it is accessible, and would not need strict ethical issues for the letters have been posted in the public domain where everyone can access them. As highlighted before, the main focus was on the phrasal-prepositional verb look forward to and to-infinitive clauses as their complementation often pose a challenge, particularly to the L2 students. These constructions were selected until the researcher was confident that the data were saturated. As was informed by the unobtrusive content analysis method, the data were subsequently coded. This is where the written communication was classified into two columns: phrasal-prepositional verb look forward to and toinfinitive clauses to extract such structures as indicated in the following section below.

Results & Discussion
This section presents and discusses the findings on the phrasal-prepositional verb and to-infinitives. It has been stated that the study seeks to describe the status of both the phrasal-prepositional verb and toinfinitives. It further identifies the category labels and the complementation of /to/ in the phrasalprepositional verb look forward to and the infinitives. The collected data are, consequently, presented in table 1 below.  (2022) Table 1 presents the phrasal-prepositional verb look forward to and to-infinitive constructions. It is evidenced that the word /to/ in both constructions are identical in terms of form, pronunciation and orthography; however, their grammatical functions are different. Such difference can be described by grammaticalisation within the MP as explained earlier. Again, it is observed that the complements of /to/ in both constructions are highlighted to mark the difference, so the complements of /to/ in the phrasalprepositional verb look forward to are DPs (nouns, pronouns) and gerunds as noted earlier while /to/ in the infinitive constructions is complemented by the verbs in their base form, that is, without any kind to inflection.
Having presented the results, it is worth noting that this section on the grammaticalisation of /to/ is subcategorised into the preposition /to/ in the phrasal-prepositional verb look forward to and the infinitive marker /to/. Data reflect that there is a great shift, commonly known as syntactic or categorial change of the word /to/ in both the phrasal-prepositional verb look forward to and infinitives. This change is known as grammaticalisation, which deals with the category change and constituent structure. According to Baybee (2011, p. 3), grammaticalisation is the re-analysis, which involves change in organisation of constituent or category membership. Change in category membership is known as decategorisation (Hopper (1991) cited in Baybee 2011, p. 3). Roberts and Roussou (2003, p. 2) define grammaticalisation as creation of new functional element that entails categorial re-analysis of the lexical or functional element. In addition to decategorisation, grammaticalisation also involves expansion and desemanticisation. With reference to Lindfors (2003, pp. 11-12), expansion in grammaticalisation refers to assigning 'an existing grammatical unit and additional grammatical function' while desemanticisation is the loss of the original semantic content. According to Duffley (1992, p. 16), /to/ shows direction and location, thus assigning grammatical case (dative case -the function of indirect object) (Brinton, 2000, p. 131;Rhee 2017). Nevertheless, there is a shift from spatial sense to temporal sense, purpose in infinitives, as well as metaphorical connection, which applies to both the phrasal-prepositional verbs and infinitives.

/To/ in the phrasal-prepositional verb look forward to
In this study, it has been emphasised that the inclusion of adverbial particles in the phrasal verbs, prepositions in the prepositional verbs and simultaneous inclusion of both adverbial particles and prepositions in the phrasal-prepositional verbs changes the meaning of such constructions, that is, their inclusion leads to acquisition of new meaning. For instance, phrasal-prepositional verb look forward to has acquired new meaning -idiomatic metaphorical meaning (Ella & Dita 2017), which has nothing to do with its components, look, forward and to as exemplified in (3) below.
(3) a. I look forward to calling you in a few days.  (3), the phrasal-prepositional phrases look forward to in (3a) and looking forward to in (3b-c) mean to expect and basically hope to enjoy something that is going to happen in future, or to anticipate with pleasure (Courtney 1983, p. 1). This implies that the anticipation of joy comes from calling you, meeting you and attending Example University correspondingly. Again, the complements of look forward to in example (3), calling, meeting and attending are gerunds as the prepositions including /to/ are always followed by either gerunds (verbs ending in -ing, which function as nouns) or noun phrases. In these examples, the preposition /to/ in look/looking forward to, does not reflect any direction or location due to its complements, which express future meaning. Therefore, the study concludes that the preposition /to/ in the phrasal-prepositional verb look forward to is affected by desemanticisation. This process of grammaticalisation is influenced by its complementation -gerund, through assimilation as /to/ no longer denotes direction but has something to do with futurity. The category label of /to/ in the phrasal-prepositional verb look forward to is, therefore, shown in examples (4) below.
(4) The category label of /to/ in the phrasal verb look forward to Example (4) demonstrates the structure of the phrasal-prepositional verb look forward to hearing from you. The structure is derived from the bottom-up, which is the feature of the MP (cf. Tjabaka 2021; Tjabaka & Morato-Maleke 2021). This means that the elements were first generated from the bottom to the top through operation merge as highlighted earlier. Therefore, the pronoun (PRN) you has been merged with the preposition (P) from to form the prepositional phrase (PP) from you. The resultant phrase is further merged with the verb (V) hear to form the VP hear from you, which is later merged with gerund/gerundive (G) morpheme /-ing/. To form gerund phrase hearing from you, the G affix -ing is later lowered through affix hopping to be attached to the V hear to become G hearing. Subsequently, the GP is further merged with an adverbial particle (Adv) forward to form V-bar (Vˈ) forward to hearing from you. Thereafter, the Vˈ is merged with the V look to form the VP look forward to hearing from you. This phrase is later joined to null tense (T) category to form T-bar. The T-bar is further merged with determiner (D) I, and the resultant phrase of the whole clause is TP I look forward to hear form. It is, therefore, indicated that the structure of the phrasalprepositional verb look forward to is VP, and this finding has also been observed in Yuliastuti's (2008) study. This is because it is headed by such phrase. In the similar structure, the category label of /to/ in the phrasalprepositional verb look forward to is identified as a member of preposition, which is complemented by a gerund.
Even if the structure of the phrasal-prepositional verb look forward to also changes, the category label of /to/ in such constructions is still the same -preposition. In example (5) below.

Categorial Conflict between Phrasal-Prepositional Verbs and
Infinitives: The Great Complement Shift

(5) The category label of the phrasal verb look forward to
Assuming that the phrasal-prepositional verb look forward to (transitive ergative structure) has three-place predicates: the external argument I and the internal arguments hearing and from you in example (5), ternary branching is not used to accommodate the three arguments as such branching violates merging. Merging adapts binary branching. Therefore, to accommodate the notion of the three-place predicates without violating the operation merge, the VP has to be splitted into outer shell and inner core, hence verbaliser phrase (vP) and VP (Radford 2009, p. 292). For this reason, the structure in example (5) is vP while the category label for /to/ is still P. The sentence, I look forward to hearing form you, is still derived from the bottom using the similar operation, which is merging. The gerundive suffix /-ing/ is also lowered to be attached to the verb hear through the affix hopping. The only remarkable issue here is that, in order to interpret the subjects that are not pronounced, the researcher has used the VP-Internal Subject Hypothesis (VISH) and Predication Principle.
On the issue of the VISH, the subject originates from the VP (Tjabaka 2021) and moves successively to check Extended Projection Principle (EPP) attracted by T. The subject I, also known as specifier, has moved from the specifier in lower TP [spec, TP] to higher [spec, VP] to satisfy Predication Principle, which states that we should consider the number of predicates place that each verb has in a sentence. Therefore, looking at the example (5), the verb look has an external argument as one of the place predicates, that is, it requires someone who does the action of looking. Then, the specifier I moves again successively to occupy the position of the subject of the whole sentence where it is assigned nominative case. Even if assimilation (between the preposition /to/ and its complement hearing, which is in gerundive form), has occurred to change the meaning of /to/ in example (5), that has not affected the categorisation of /to/, hence it is still labelled as preposition. Thus, it is affected semantically, not syntactically.
In line with the complementation, the prepositions are basically followed by the DPs and gerunds as highlighted before. Therefore, it should be emphasised that the phrasal-prepositional verb look forward to is not an exception as it is not only complemented by the gerunds, but also the DPs as illustrated in example (6) below. https://journal.unilak.ac.id/index.php/elsya 167 Categorial Conflict between Phrasal-Prepositional Verbs and Infinitives: The Great Complement Shift

b. I look forward to [your reply].
Example (6) demonstrates the phrasal-prepositional verb look forward to and its complements. In both constructions, the complements are DPs a positive response and your reply, respectively. Their structures, as well as the category label of /to/ are still the same as the gerund complementation. This evidence is given in example (7) (7) DP complementation of the phrasal-prepositional verb look forward to (Recorded as example (6a), but repeated here as example (7)  In example (7), the structure of the phrasal-prepositional verb look forward to is the VP because such phrase is headed by the VP. In the same phrase, /to/ is still a member of preposition. Similarly, the preposition /to/ does not implicate any meaning of direction or location. Just like the phrasal-prepositional verb look forward to constructions that are complemented by the gerunds, the phrasal-prepositional verb look forward to constructions, which are followed by the DPs also have idiomatic figurative meaning. For instance, the writer of that application letter anticipates that joy would come from a positive response.

The infinitive marker /to/
It has been indicated that the study also concentrates on the structure of the infinitives, the category label of the infinitive marker /to/ and its complement. This aspect has been used starting from the OE era to the present. The infinitive marker /to/ has undergone some changes and modification through various periods. It has been shown that Verba (2004, p. 62) stipulates that to-infinitive in the OE was referred to as the verbal noun and had grammatical category of cases such as nominative and dative cases. According to van Gelderen (1993, p. 85), initially, the infinitive marker /to/ was a preposition that expressed dative to signal direction 'together with an ending on the infinitive' with its idiosyncratic ended -an/-ian (Miller 1902;Verba 2004). For both nominative and dative cases, the infinitive was arranged as shown in (8) However, during the ME period, the ending of the infinitives was lost, but the infinitive marker /to/ remained. Therefore, /to/ had to be re-analysed, and due to desemanticisation and grammaticalisation, its category changed from the preposition to auxiliary (van Gelderen 1993, p. 86). According to van Gelderen, these two processes denote gradual vicissitudes turning the preposition to into auxiliary category where the P to was also included, preceding the whole form of dative case (Duffley 1993). The arrangement was, thus: (9) to + base verb + suffix -enne or -anne to + play + -anne > to pleyanne/pleyenne During the ME, the literature has affirmed that the structure of the infinitives changed from nominal to verbal parts of speech, and both -an and -ne weakened to -en and -e, correspondingly. The P to had also lost its lexical meaning. Both Duffley (1993) and Verba (2004) affirm that the dative ending -ene, which deeprooted the case-assigning prepositional status of to vanished gradually. Therefore, the P to had then lost its dative case-feature acquiring a pre-infinitive particle to. It is, then, concluded that starting from the ME until the present, the structures of the infinitives have changed; that is, they lost their nominal features to the verbal category thereby demising the suffixes and acquiring a pre-infinitive particle to. According to Tanaka (1997), Nakagawa (2001) and Jarad (2011), this loss has given rise to the following: to has become a Tense (T) element; passive to-infinitives; infinitive with perfective have; independently negated infinitives, exceptional case marking (ECM) or subject-to-object raising; and split infinitive constructions. In addition, the infinitive-to occurs in control infinitives; it can combine with higher complementisers for and whether; and it mainly follows an overt subject (Robert & Roussou 2003, p. 98) It could be inferred that the category of /to/ in the infinitives changed from the P to the T as shown in example (10)  Example (10) reflects the structure of the infinitive clause and the category label given to the infinitive marker /to/. In this example, the infinitive clause to further discuss my qualifications is the complement of the passive structure, where the passive verb considered is moved from the V position to be spelled out as the light verb or verbaliser. Following Runner's (2006) view on a covert raising, same thing happens to the D I, which has been moved and deleted from the embedded clause TP I to further discuss my qualifications -lower [spec, TP] and pronounced in the main clause, higher [spec, VP]. Therefore, the structure of the infinitive clause is the TP. The issue that the D I originates from the embedded infinitive clause emanates from the notion of the subject-to-object raising issue raised by Tanaka (1997), Nakagawa (2001) and Jarad (2011).
Again, the evidence that the structure of the infinitive clauses is the TP is also supported by Tjabaka (2021) and Tjabaka and Morato-Maleke (2021) who also have a view that the structure of the infinitives is TP. The result is influenced by the fact that the infinitive marker /to/ has acquired temporal sense, that is, 'an event to any point in time prior to its realisation' (Duffley 1992, p. 17). This means that the infinitive markers /to/ denotes futurity and unrealised or hypothesis, also known as future irrealis (Duffley 1992;Wurmbrand 2014). In the example (10), there is an element of futurity where the action of discussing is expected to be done some time in future. For this reason, the infinitive marker /to/ is, indeed, a member of the tense (T) category. This finding conforms to Tanaka's (1997), Nakagawa's (2001) and Jarad's (2011) studies that the infinitive marker belongs to the T category. The categorial change of this infinitive marker is known as decategorisation: changing from the preposition to the tense. Moreover, since the infinitive marker /to/ has also acquired/gained another label and grammatical function, it has undergone the process of expansion. This means that, indeed, there is a grammatical change in /to/ of the infinitive clause.
Besides the structure and category label, the complement of the infinitive marker in English is a verb in its base form. This means that it is not inflected for tense, gender and number. The study has depicted that from the ME to the present, the infinitives allow split constructions. As a result, it is observed that in example (10), the infinitive construction is splitted by an adverb further, followed by the verb discuss, which is in its base form.
Earlier, the researcher has emphasised that the structures are generated from the bottom-up. Therefore, this paper builds on Adger's (2002, p. 108) and Tjabaka's (2021) opinion that verbaliser (v) is an extension of the VP projection, hence the structure exemplified in (11) below. Example (11) represents the structure of the infinitive clause to join your company. Unlike the structure of the infinitive clause in example (10), whose structure is TP, the structure of the infinitive clause in example (11) is vP, making the infinitive marker a member of the verbaliser. The structure of the infinitive clause and category label of the infinitive marker /to/ are also identified by Čakányová and Emonds (2017) and Čakányová (2018) who have used Denison's (1993) negation, inversion, coda and ellipsis (NICE) criteria to determine the structure of the infinitives and the category label of the infinitive marker. The present study also argues that the structure of the infinitives can also be the vP, and that the category label of the infinitive marker /to/ belongs to the verbaliser. However, this paper departs from the NICE criteria and dwells on the notion of merge and the extension of the VP to describe such structure. The current study even builds on Adger's (2003:108) argument that conceptually, v and VP have relations such that whenever there is a verbaliser (v), there is also its VP complement. He further indicates that intuitively, the vP is an extension of the projection of VP. This implies that the vP to I join your company is extended from the VP I join your company. As also demonstrated in the construction of the phrasal-prepositional verb look forward to, the movement of the specifier I is also successive, and it originates from the lower VP and moved as it is attracted by the EPP and has to show the predicates-place that each verb has.
It is worth noting that the idea that all the multiple specifiers in the given examples are not deleted is supported by the Movement Theory of Control of the MP, which stipulates that one argument can bear multiple roles.

Conclusion
The study has aimed at describing the status of both the phrasal-prepositional verb and to-infinitive clause. It has also sought to determine their structures and identify the category labels of /to/ in the phrasalprepositional verb look forward to and the infinitive marker /to/ and their complementation as a way of resolving their categorial conflict. The evidence has shown that /to/ in both the phrasal-prepositional verb look forward to and to-infinitive clauses have undergone a great shift known as the process of grammaticalisation. However, with the one in the phrasal-prepositional verb look forward to, syntactically, it is still categorised as the preposition. However, it has acquired idiomatic metaphorical or figurative meaning that has an element of time, particularly if it is complemented by the gerunds. This shows that it has undergone through desemanticisation. On the other hand, the category label of the infinitive marker /to/ has undergone the processes of decategorisation and expansion, which is why its category label varies depending on the theory adopted and certain concepts of the certain theory. Regardless of the differences between the two (the phrasal-prepositional verb look forward to and to-infinitive clauses), there are some similarities with regard to the structures. The study concludes that this only happens if the focus lies on the transitivity of the verb look in the phrasal-prepositional verb look forward to, and when the researcher concentrates on the extension of the VP. Besides this, the structures are different as look forward to is the verb phrase (multiple verb) as suggested earlier while the to-infinitives are clauses, which is why their structures even differ depending on the concepts of the theory adopted. The other difference is spotted in the complementation where the phrasal-prepositional verb look forward to is complemented by the gerunds or DPs whereas the infinitive marker /to/ is complemented by the verb in a base form. It is further concluded that due to grammaticalisation of /to/ in both phrasal-prepositional verb and infinitive, their complementation differs. The study took note that the preposition /to/ in the look forward to construction does not denote direction or location but has an element of time. Therefore, it is suggested that more research should be done to find out if the process of assimilation has not influenced the categorisation of /to/ in the phrasal-prepositional verb look forward to.