'I am to go'

'To' is with 'go' here like working as an Infinitive

I am to go. or it is with 'am' like 'am to'

I am to go.

Same question for 'supposed to + verb' and ' have to+ verb'.

I know when to use these sentences and the meaning it gives....but I don't understand its structure.

  • "To" is not part of the verb. "To" is a separate constituent, a subordinator functioning as a marker for VPs of infinitival clauses. For example,in "I am [to go]", "to go" is an infinitival clause as complement of "am", consisting of just the predicate VP "to go", which consists of two constituents, "to" (marker) + "go" (head VP) .
    – BillJ
    Apr 1, 2021 at 8:01
  • Incidentally, "supposed" is not a verb in your example, but a participial adjective.
    – BillJ
    Apr 1, 2021 at 8:36

3 Answers 3


I am [to go].

English does not have an infinitive form of the verb in the way that, say, French does. "To go" is not a verb; it's two words, the subordinator "to" and the verb "go". "To" is a separate constituent, a subordinator functioning as a marker for VPs of infinitival clauses.

In "I am [to go]", "to go" is an infinitival clause as complement of "am", consisting of just the predicate VP "to go", which consists of two constituents, "to" (marker) + "go" (head VP)

  • 'To go' here is a complement of 'am'........but 'am' is a linking verb and often subject complement comes after it......so 'to go' should be a complement of subject ......not a verb complement. But If i take it as a subject complement it will change the whole meaning of sentence.
    – RADS
    Apr 1, 2021 at 8:36
  • 1
    No: predicative complements are adjectives or nouns, not clauses. "To go" is catenative complement of the verb "be" ("is"). It's a complement because it is required to complete the VP.
    – BillJ
    Apr 1, 2021 at 8:40
  • Okay so subjective complement are also called Predicative complement and it can only be adjectives and nouns....I have two questions from here .......1. Objective complement and Verb complement can also be called Predicative complement.....or they r called sth different............2. Gerund and participle (working as Adjective) can be called subjective complement....
    – RADS
    Apr 1, 2021 at 8:48
  • 1
    @RADS Not quite: Subject and object complements (PCs) are both complements of the verb, though they refer to the subject or object, of course. Verbs (VPs) can't be PCs, but gerundial nouns and participial adjectives can, as in "What I hated most of all was the killing" (PC-noun) / "The show was very entertaining" (PC-adj).
    – BillJ
    Apr 1, 2021 at 9:38

There have been many different approaches to the grammar and semantics of the syntax of the kind of I am + to infinitive.

Though, there are the basics of the theory of the verb-link sentences. The syntax of the constructions I am +to infinitive and I am + present participle are the same, it is Subject + Verb‐link + Subject complement intrinsically.

Subject complement in the construction may be a nonfinite verb, but not limited to nonfinite verbs only.

The infinitive and present participle belong to the nonfinite verbs grammar set. In case of the present participle it is the grammar construction of Present Progressive, or the Present Continuous Tense, if you like. Present Progressive has been described in numerous textbooks and is a well-known topic. That is why we omit further depiction of the construction Subject+Verb-link+Present participle and devote the further short depiction to the the construction Subject+Verb-link+Infinitive.

The modern English grammar defines a Subject complement as the information that describes, identifies, or renames the subject of the clause. For example, the well-known sentences from grammar textbooks follow:

  1. This suit is grey. Or, a grey suit. The Subject is modified to a new meaning.

  2. Politicians are those who create the laws. Or, lawmakers. The Subject is renamed,or identified.

  3. The computer is his. Or, his computer.The Subject is modified to a new meaning.

  4. The man is well-dressed. Or, a well-dressed man.The Subject is modified to a new meaning.

  5. He is to read the book. Or, a man under obligation of reading the book. The Subject is modified to a new meaning. The modifier is a Prepositional phrase.

Many authors consider the verb 'to be' in (5) as a kind of a modal verb. Such an introduction is for the purposes of learning only. And, sometimes this can draw away from understanding some true semantics and grammar of the Construction.

The reasons of such inference are obvious: 1. the verb to be is a linking verb that functions as an auxiliary verb in the Construction; 2. linking verbs of both types, to be and to become, cannot be modals because they are finite verbs themselves in the Construction, and the sentences, for example, This must be a useful tool, or This has been a useful method for long are usual and grammatical in the modern English language.

To sum up, we can conclude that the sentence I am to read the book is identical to the Subject modified with the adjectival prepositional phrase, the man under obligation of reading the book at the ongoing time semantically.

  • @ Ingram Thankyou.... What about the construction 'have /has/had+ to-infinitive'?...how the Infinitives work here.... please also add its answer.
    – RADS
    May 28, 2021 at 16:22
  • @RADS It is possible to write on the topic you've requested. Though, it could be a distractive text from the instructive standards. To know English properly on practice, you should concetrate on the idiomatic usage and semantics of the construction have to instead of theoretical hair splitting. I can add just that it is not a linking verb grammar, it relates to the lexical verbs with complements branch of the English grammar. That's why it seems to be better to open a new page, and inform me, if you like.
    – kngram
    Jun 4, 2021 at 10:12
  • The sentence: '"Officials say the soldiers were outnumbered and their instructions were not to intervene." The sentence is an example of investigative and watchdog journalism which is frequent with grammar ellipses. The complete syntax of the clause is that '..the instructions were the soldiers to not intervene.' The Infinitive is a Postmodifier in the noun phrase which is the Subject complement in the clause in its turn.
    – kngram
    Sep 15, 2021 at 15:56

In these cases, the word "to" is part of the infinitive verb phrase. And the infinitive verb phrase "to go" is the complement of "I am..."

The same is true with "supposed to" and "have to", but in all cases, and particularly with "have to" the combination becomes idiomatic, to the point that "have to" functions almost as a modal verb, especially when the actual verb is deleted.

I want to go fishing, but I'm not supposed to.

I want to see my aunt and next week I am to.

But this is odd syntax. The use of "I am to ..." is dated and rare and this deletion just makes it hard to understand. You would just say "...next week I will".

  • A couple of things, James. "To" is not actually part of the verb itself, but a separate constituent, a subordinator functioning as a 'marker'. And I'd say that "supposed" is a participial adjective.
    – BillJ
    Apr 1, 2021 at 8:34
  • sure, "marker", "clitic", "particle" I've seen the "to" described as all these things. Yes participle adjective is reasonable. The semantic point is that the connection to the verb "suppose" is tenuous at best,
    – James K
    Apr 1, 2021 at 8:54

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