The 'to infinitive' has the structure to + verb as in to go, to eat, to ride, etc. The word 'to' is thought to be a preposition. However, since a preposition needs an object and a verb cannot be an object, can 'to' be more of an adverb, since it modifies a verb in the structure? An adverb modifies a verb.

W R T: The word “to” in “to succeed” is a preposition-particle (some call it a particle, others a preposition – these really refer to the same thing); we see the following: A preposition needs an object which is related to a noun or a pronoun in a sentence to satisfy its definition.

An object in a sentence is also usually a noun or a pronoun; though there can be others like the 'that-clause', the 'where- clause, etc. The object receives the action done by the subject.

In a phrase like the following which has the 'to infinitive' [notice that 'to' is part of this verb phrase (and keeping in mind that a preposition usually does not modify a verb)] :i.e; in, I want to go; go is a verb and cannot be the object of the preposition.

In: I look forward to meeting you; 'meeting you' is not an object; etc.

Thus, since the to-infinitive has the structure: to + verb, and the verb cannot be an object- it is more of a state or intention or an action- 'to' in this structure cannot be a preposition. If it is definitely not a preposition then since it modifies a verb, indicating an 'intention', and an adverb by definition modifies a verb, 'to' is an adverb.

  • Give us a specific example. Oct 24, 2014 at 16:55
  • To is still a preposition. It goes with the preceding clause so it can have the verb after it. It in no way modifies or qualifies the verb, unlike an adverb. It helps as an alternative to using the gerund form of the verb at times.
    – Kris
    Oct 24, 2014 at 17:00
  • Too is an adverb; to come to (to gain consciousness) is an adverb; to eat is possibly a preposition, or, perhaps better, an infinitive maker. Oct 24, 2014 at 17:09
  • @Gary'sStudent: I assume this is about coffee to go, ticket to ride and the like. In which case it's kind of a duplicate of A coffee to go…( for syntax experts)
    – RegDwigнt
    Oct 24, 2014 at 17:33
  • 1
    It would be simpler to invent a new term for "to" before an infinitive. I use infinitive-particle. With this term I avoid the complication you have when you call "to" before an infinitive a preposition. Historically the infinitive has noun character and "to" was a normal preposition.
    – rogermue
    Oct 24, 2014 at 18:45

2 Answers 2


The to in the full infinitive is considered a grammatical particle, i.e., a word that does not serve a part-of-speech function by itself, but only in combination with another word in the sentence.

  • More correctly, an "adverbial particle," according to that school of thought. That brings us back to square one: is it or is it not an adverb? This theory is no help in answering the present question.
    – Kris
    Oct 24, 2014 at 17:27
  • How can something that does nothing be a modifier?
    – Kris
    Oct 24, 2014 at 17:29
  • 1
    As I said, the particle by itself has no part-of-speech function. Therefore it makes no sense to call it "adverbial", "prepositional", or anything like that. The two words together, say "to eat", serve as a nonfinite verb. Oct 24, 2014 at 17:33
  • Other examples of particles are in some phrasal verbs, such as the word "up" in "he's given up on life." Oct 24, 2014 at 17:33
  • @Kris You're assuming that 'particle' is well-defined. I'd label this the to-infinitival particle if I had to fine-tune. This 'to' behaves nothing like any sort of adverb I'm aware of. It marks rather than modifies the bare infinitive. Contrast 'boldly' in ' ... to boldly go ... '. Oct 2, 2020 at 15:30

You are all correct. The key is to not think of the infinitive as a standalone part of speech, but a functioning unit of language. Look at the phrase's function, and it will show the part of speech. It will be a noun, adjective, or adverb.

Examples: Noun --> "His job was to help me." (What was his job?)

Adjective --> "There is a file to turn in your resume." (Modifies or describes the file)

Adverb --> "I went home to take a bath." (Why did you go home?)

  • Fine until 'Look at the phrase's function, and it will show the part of speech.' POS-tags apply to lexemes. A phrase may be adverbial, but few would label it an adverb. Oct 2, 2020 at 15:33

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