In English, is the infinitive marker a part of speech? I noticed that Oxford was using it in the PoS lexical entry position for one sense of "to": https://en.oxforddictionaries.com/definition/us/to

"Bob wants to eat pizza."

If not, is it a particle - and the particle is a part of speech?

  • Yes, it's a part of speech. In CGEL, it's analyzed as a subordinator, whose primary function is that of marker of subordination. Apr 19, 2019 at 16:20
  • The infinitival 'marker' (function) belongs to the part of speech 'subordinator'.
    – BillJ
    Apr 19, 2019 at 18:21
  • @BillJ Doesn't a "subordinator" take a full clause as its argument, not a VP?
    – Draconis
    Apr 19, 2019 at 20:28
  • 1
    +1 But you really need to wait a few days before accepting an answer on here. Otherwise people who might otherwise spend time writing you an answer may not bother to. (That's the situation with me, for example, right now) Apr 19, 2019 at 23:28
  • "To" is a special marker for the VPs of to-infinitival clauses.
    – BillJ
    Apr 20, 2019 at 6:44

2 Answers 2


It turns out, "parts of speech" are one of those formalisms that's taught in all the schools, but isn't always useful when you start looking closer.

Fundamentally, "part of speech" is a word's role in the syntax. "Walk" and "run" and "go" and "travel" all act pretty much the same, syntactically, so it makes sense to say "all of these things are Verbs, and this is how Verbs act". And then you find words like "eat" that act almost the same, but not quite, so you separate them into "Intransitive Verbs" and "Transitive Verbs", and write some rules about Intransitive Verbs and some about Transitive Verbs, and some about all Verbs in general.

But this stops being useful when words act, syntactically, like nothing else in the language.

The "infinitive to" appears in only one construction. It takes the bare form of a verb, and turns it into either a non-finite verb or a verbal noun, depending who you ask. And there's no other word in English that can do the same thing. It looks just like the "preposition to", but it doesn't act as a preposition: you can't say *he wants for go now, or *he wants behind go now.

So, historically, the solution was to call it a "particle"—where "particle" means "we don't know what category to put this in, but it needs a category". (In English at least: in a few languages, "particles" are a legitimate category of words that all act the same.) But as far as actually doing syntactic analysis, I'd just keep it in a class all of its own, which is what most POS-taggers will do: the Penn treebank, for example, gives it the special tag TO shared with no other word.

  • Historically the Infinitive particle "to" was a preposition for the inclined form. For example: drinkan - to drinkenne.
    – user307254
    Apr 19, 2019 at 8:39
  • The infinitival marker "to" belongs to the category (part of speech) subordinator.
    – BillJ
    Apr 19, 2019 at 18:23
  • @user307254 the inclined form sounds so much like Saxon :) btw, German zu is like to for the subordinate clause, "Ich wünsche zu trinken". That shouldn't be confused with the English infinitive marker to and much less the preposition, but isn't that exactly what happened for English? Similar confusion gives etwas zu trinken; zu trinken; Trinken. The preposition can appear in verbs, zuschauen, thus reduplicating um zuzuschauen. German doesn't have any infinitive marker (the infinitive is homophone with 1. and 3. p. pl.). Why label infinitives at all, unless for dicts?
    – vectory
    Apr 19, 2019 at 19:58
  • @user307254 Interesting, Latin also formed its infinitives out of an inflected form of the verbal noun (I think it was a locative for the active and a dative for the mediopassive).
    – Draconis
    Apr 19, 2019 at 20:36
  • @billj Not according to Pullum, or many others. Apr 19, 2019 at 23:21

Of course, the infinitive marker to has a part of speech (POS) label. What exactly it is depends on your POS tagset. In the Penn Treebank tagset there is a special tag TO only for the infinitive marker (sometimes merged with the preposition depending on the corpus and the tagger used), in another tagset is may be just a PART (particle) togeter with other particles of different rôles.

  • It belongs to the category (POS) subordinator. Marker is its function, not its POS.
    – BillJ
    Apr 19, 2019 at 18:24
  • @BillJ Huh? That sound like very special terminlogy not shered among the people dealing ith part-of-speech tagsets. Apr 20, 2019 at 17:49
  • Who's talking about 'tagsets'? The OP certainly isn't (look at his question). H&P discuss this in GGEL, where they demonstrate that 'subordinator' is preferable to ''defective verb' (the only other possibility).
    – BillJ
    Apr 21, 2019 at 6:32

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