The following are correct:

  • I want to eat this.
  • I want to! (e.g. in response to a suggestion)
  • I forgot to do it.
  • I forgot to! (e.g. in response to “Did you do it?”)

However, while the following are correct:

  • I look forward to eating.
  • I look forward to it!
  • I’ve changed my mind about eating.
  • I’ve changed my mind about it!

The following are obviously wrong:

  • X I look forward to!
  • X I’ve changed my mind about!

Why? What’s the underlying rule here? I have a vague idea but would like a proper grammatical explanation since I’m trying to help an English learner who asked me this question. Thank you!

  • look forward to what? Changed my mind about what?
    – user405662
    Mar 2 at 11:29
  • 4
    Syntactically, "I look forward to eating" is the same as "I look forward to the party". In both cases, to is a preposition before a noun. That's completely different to "I want to eat [this]", where to is the infinitive marker (in a context where the infinitive verb eat can optionally be followed by an object - the thing to be eaten). Mar 2 at 12:31

2 Answers 2


This question has to do with ellipsis. After "to" can be ellipted to-infinitive clauses, but not other grammatical elements. That is just a matter of usage. This can be deduced from A Comprehensive Grammar of the English Language by Randolph Quirk et al. in the chapter "Pro-forms and ellipsis".

  • He wanted to study physics, but she didn't want him to (study physics). ("Study physics" is the ellipted part, which, if kept in the sentence does not make it incorrect, but it is then a rather unusual one.)

  • Babies have to crawl before they walk; it is pretty obvious that they have to (crawl).

(OALD) to look forward to [ (user LPH) This verbal form is constructed with a noun phrase after "to" or an -ing-clause, not an infinitive clause.]

  • I am looking forward to the weekend.
  • We're really looking forward to seeing you again.
  • She was looking forward to become a full member.

There is no possible ellipsis after "about" (usage).

  • Thank you for this explanation and for recommending these resources. As I suspected, “to look forward to” takes a noun phrase, and while we can use “it”, we cannot omit the noun phrase. I wanted to ask, what is “study physics” in “I want him to study physics”, is it (part of) a verb phrase? Because if so, it seems like we can say that we can ellipt a verb phrase to “to”, but not a noun phrase? If this is correct, it might serve as a good general answer.
    – localflorist
    Mar 2 at 11:46
  • 2
    "To study physics" is a to-infinitive clause, which is a type of non-finite clause, so called because the verb form is not conjugated (to study, studying, studied). That is right, after "to" you cannot ellipt nouns, nor can you ellipt -ing-clauses.
    – LPH
    Mar 2 at 11:51
  • That clears it up enough for me, thanks so much for your help! :)
    – localflorist
    Mar 2 at 11:56
  • 2
    It’s somewhat implied in the answer, but I think it’s worth spelling out that the to in ‘I want you to [infinitive]’ and the one in ‘I look forward to [noun/gerund]’ are not the same word – they just happen to look the same. In the former, to is a particle marking that the following verb is in the infinitive; in the latter, it is a preposition that takes a nominal entity (pronoun, noun phrase, gerund, etc.). ‘I look forward to going’ is structurally completely parallel to ‘I prevented him from going’, just with a different preposition. Mar 2 at 20:33
  • @JanusBahsJacquet The point of view I'm familiar with (that in the grammar I quote and also in OALD (OLD online)), is that a verbal form suxh as "to make" is called a "to infinitive" (the term "splitting infinitives", which should really be "splitting to infinitives" shows clearly that the particle is part of the verbal form) and the form "make" is the bare infinitive, also called the base form; this corresponds however to your understanding that "to" would be a particle empty of meaning. However, if this is sometimes true, it is not quite so simple: there is a certain duality (1/2)
    – LPH
    Mar 2 at 23:23

Infinitive clause complementation and non-repetition of the main verb (in spoken English).

There are four categories of verbs that trigger infinitive complementation: Verbs of intention: plan, mean, aspire, aim, propose, wish, resolve, long, promise, vow. Some of them do not require repetition of the main verb:

  • Verbs involving atttempting to do something: begin, attempt, forgot,

[this answer is UNFINISHED, Will finish a bit later. Thanks]

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