I teach ESL at the adult level. I am trying to analyze "used to" for past habitual, as in:

  • My car used to malfunction a lot.

Is "used to" an adverb-phrase meaning something like 'for a long time in the past'? Or is it a finite verb?

If it's an adverb-phrase, it's worth noting that we don't have a past-tense main verb, as:

  • My car used to malfunctioned(sic) a lot.

Perhaps that's evidence that "used to" is actually a finite verb?

I believe I may have read somewhere that "used to" evolved from "was/were used to" (meaning 'was/were accustomed to'); however, if this be the case, then I would expect a gerund instead of a base infinitive, as:

  • My car used to malfunctioning(sic) a lot.

I'll appreciate any insights.

  • Used to is an idiom; in fact, there are two idioms pronounced alike but with different syntax and meaning. This one is a past tense construction with special presuppositions. It's very common in speech, but in writing it's not used as often because there's a certain confusion about the past negative spelling: "didn't used to" or "didn't use to"; neither one feels good. But then English spelling sucks, as everybody knows.
    – jlawler
    Jun 9, 2016 at 15:26
  • If we're going to say that "used to" is actually the finite verb in the sentence, and if we're going to say that the "-ed" makes it past, then it seems we would want to write "didn't use to" (with no D). On the other hand, if we're going to say that the "-ed" is something else, like the participle/adjective "-ed" in "accustomed to", then it should not come off when we use aux. "did". But if that were the case, then we wouldn't use "did" as the aux; we'd use "was/were". This makes it appear to me that "used to" is likely the finite verb. Jun 9, 2016 at 17:03
  • I'm not sure whether used to should be considered finite or not. It doesn't inflect worth a damn; rather, it's got the same kind of tense as modal auxiliaries and their periphrastic equivalents -- hafta, gonna, wanna, oughta, gotta, and their ilk. Except it triggers Did-Insertion with negative contractions.
    – jlawler
    Jun 9, 2016 at 18:18
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    Why is everybody making this so complicated? It seems to me to be a simple past tense verb (used) with an infinitive (to malfunction). No different from tended to malfunction or needed to malfunction. In this case use means "to be accustomed to or in the habit of." We just confine its use to past tense, except for in the negative, and always combine it with an infinitive.
    – Tom
    Jun 11, 2016 at 22:13
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    "used to" is a phrasal modal, an auxiliary. This is an often-overlooked part of English grammar.
    – William
    Sep 24, 2016 at 21:29

2 Answers 2


Preliminary point: The verb-form is the single word "used", not *"used to". Take your example:

My car used [to malfunction a lot].

The bracketed sequence is a non-finite clause acting as complement to "used". "To" belongs in the complement clause; it's simply a marker, a subordinator whose function is to mark to-infinitival clauses.

No, it’s not an adverb phrase. The 'main' verb is the auxiliary verb "used"; it’s a tensed verb-form, more specifically a past tense form. Auxiliaries are primary (tensed) verb-forms, for example “might”, “could” and “should” are respectively the past tense forms of the present tense forms “may”, “can” and “shall”. Note, incidentally, that although “use” is an auxiliary, it is semantically quite distinct from the modal auxiliaries; the meaning it expresses is aspectual, not modal.

“Use” is highly defective; it has no present tense, only infinitival and past forms, so although the form “use” appears to be a present tense form, it is in fact the infinitival form which is only used in negatives and with inversion: He didn’t use to smoke; Did he use to smoke?

There is the added complication that “use” can be a lexical verb or an auxiliary one, though the books tell us that many speakers treat it as a lexical verb. I suspect that’s due to the unacceptability for many people of the auxiliary use found in %Smoking usedn’t to be allowed and %Used he to smoke?

Lexical Use (infinitival verb-form + do-support required in negatives and questions):

He used to smoke. He didn’t use to smoke. Did he use to smoke?

Auxiliary Use (past tense verb-form, no do-support required)

He used to smoke. %He usedn’t to smoke. %Used he to smoke?

(% = acceptable in some dialects only)

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    For what it's worth, I'd point out that use in this sense began life as a lexical verb - you find it fully inflected for instance in the AV "Look thou upon me, and be merciful unto me, as thou usest to do unto those that love thy name," and this persists into the 19th century. I suggest that the anomalies and quarrels over negative and interrogative forms are effects of its (still incomplete) evolution from lexical to quasi-modal; hafta exhibits the same conflicts. Perhaps we should call these "Hunchback" verbs! :) Jun 13, 2016 at 16:58
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    @Araucaria I wouldn’t go along with that. In construction with auxiliary “do” as in Did he use to live alone? “use” can only be the plain form, but that’s the only place it’s found. And “used” is clearly an inflected form of “use” to give the past tense. The uncertainty about the form of the past tense, as in He used to smoke probably arises because (as you allude to) “used to” is pronounced with a single /t/ and hence is homophonous with the “use to” in He didn’t use to smoke.
    – BillJ
    Jun 13, 2016 at 17:09
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    Incidentally, for those who resent the criticism being levelled at "use" for having dual status as both a lexical verb and an auxiliary one, there's some comfort to be had from the fact that "use" is not alone; for example "need", "dare" and static "have" can all be auxiliary and lexical, though they have their individual peculiarities.
    – BillJ
    Jun 13, 2016 at 17:46
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    @Araucaria Hold on! So there's a homophony issue; so what, we know that. It doesn't matter. 'Facts is facts', as they say, and the tests show clearly the contrast in the syntax of aux "use" vs lexical "use". You're over-analysing.
    – BillJ
    Jun 13, 2016 at 19:44
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    @Paul L New Jr I suspect the reason that people consider “to” + “use/have” as a unit is that they are commonly used as ellipted forms of the full VP, e.g. A: “Do I really have to go the dentist”?, B: “Yes, you have to__”. Similarly, A: “Do you smoke”? B: “No, but I used to__”. In those examples, the gaps represent the ellipted words “go ” and “smoke”. But I don’t think the frequent use of such ellipsis warrants “used to” and “have to” being reanalysed as verbal idioms taking bare infinitival complements.
    – BillJ
    Jun 15, 2016 at 8:00

I don't see why this should be an adverb phrase.

Of course, the construction is highly conventionalised, probably even lexicalised and no longer productive (you probably couldn't say My car uses to malfuction a lot), but syntactically, this is a perfectly valid past tense verb which takes a verb in bare infinitive as an argument (this is why * used to malfunctioned or * used to malfunctioning is ungrammatical).
If it were an adverb phrase, what would be the finite verb in the sentence then? There needs to be one, and certainly this is used (to), due to its inflection, due to its syntactic position which is the usual default position for finite verbs and due to there not being any other possibilty to find a finite verb in the sentence, without which it would definitely be ungrammatical.

What would your arguments in favour of it being an adverb phrase be? I don't see any similarity with an AP here; used to isn't anything that modifies a averb, but is a verb itself; also, I know of no case where an AP could take a verb complex in bare infinitive as an argument (which used to does), in general adjunctions can not have any arguments (that malfunction is an obligatory argument of used to gets clear when we remove it and get an ungrammatical sentence: * My car used to); and most importantly, an adverb phrase would be merged into the syntax tree by adjunction, i.e. it would be an optional constituent which just modifies some other constituent (in case of adverbs, this is mostly the verbal phrase) but can easily be left out without this changing the grammaticality of the sentence (My car used to malfunction vs. * My car malfuction a lot).
This may hold true for a lot, but in the use of used to, this is definitely not the case, this is not just some adjunction that merely modifies its core constituents, but an a core contituent itself, namely the VP.

So I really don't think used to could in any way be analysed as an adverb phrase, and I don't see the problem of it being analysed as a finite verb, only because its use is in some way restricted and more or less lexicalised.

I must revise my claim that used to is not productive: I use to play tennis on modays is perfectly fine, and the fact that the full inflection paradigm is possible and regular (I use to, you use to, he uses to, ..., I used to, you used to, ...) I would see as another argument that used to is a totally normal finite verb, just in this context to some degree lexicalised/conventionalised and usually used in past tense.

Update 2:
The native speakers here have convinced me that my grammaticality judgement about present tense is probably wrong ;) So this doesn't seem to count as an argument for used to being a fully productive verb; but still, the other factors I mentioned are sufficient evidence in my opinion.

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    I wouldn't think that "he uses to play tennis" is at all grammatical
    – curiousdannii
    Jun 9, 2016 at 14:53
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    I'm not sure the present tense is grammatical either, I think it might just be the past tense suffix getting dropped in less formal speech. If you can show an example of "he uses to" or get another native speaker to affirm it then maybe, but for now I'd have to say you're wrong. (It could perhaps be grammatical in another dialect, but I doubt it. I don't think I've ever heard it in any dialect.)
    – curiousdannii
    Jun 9, 2016 at 15:12
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    Almost all of those are relative clauses using the normal sense of use (to utilise). They're not at all comparable. And if you're not a fluent speaker, then sorry, but you're really not qualified to judge its naturalness. :)
    – curiousdannii
    Jun 9, 2016 at 15:17
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    The fact that "I used to play tennis" is pronounced like it was spelled "I use to play tennis" -- the /z/ changes to /s/ in the idiom -- is a bug in the spelling system that also produces the aversion to the written past negative "I didn't use(d) to", in either spelling.
    – jlawler
    Jun 9, 2016 at 15:23
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    I suggest that @jlawler is right that maybe it's best thought of as another modal auxiliary verb. BTW, as an English native speaker (Australian), something like 'he uses to play tennis' is completely unacceptable for me. Jun 10, 2016 at 1:15

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