In conversation sometimes I’ll say something like this:

What’s that do?

which uses “s” as a contraction for “does”.

Is this a “real” contraction, or is it incorrect usage of a contraction?

  • cf. "D'you" or even the colloquialism/slang "whaddya"
    – Aaron F
    Commented Jun 19, 2019 at 12:26
  • Did you check a dictionary?
    – Kat
    Commented Jun 19, 2019 at 16:43

1 Answer 1


According to Merriam-Webster and Dictionary.com, "what's" is short for:

  • "what is" (What's the matter?)
  • "what has" (What's happened to the car?)
  • "what does" (What's that mean?)

So it appears that "What's that do?" is grammatically correct.

Merriam-Webster: what's

Dictionary.com: what's

  • The contractions given are "What is [noun phrase]?", "What has [past tense verb phrase] (...)", "What does [noun phrase] [present tense verb phrase]?". Other syntax is possible, and each, as far as I can tell, makes the contracted verb unambiguous.
    – CJ Dennis
    Commented Jun 19, 2019 at 7:24
  • 1
    @CJDennis: Re: unambiguous - practically speaking, yes, though theoretically you could have cases like "Who's eaten?" in which the contracted verb could be either is or has.
    – LarsH
    Commented Jun 19, 2019 at 18:40
  • @LarsH "Who's hungry?" = "Who is [adjective]?". "Who's eaten?" = "Who has [past participle]?". "Who's eating?" = "Who is [present participle]?". You're much more likely to say "Who's been eaten (by the mosquitoes)?" = "Who has been [past participle] (...)?". "Who is [past participle]?" doesn't work for many (most?) verbs, and when it does (weakly), it is better analysed as the verb being an adjective.
    – CJ Dennis
    Commented Jun 20, 2019 at 3:51
  • @CJDennis: We're mostly in agreement, practically speaking. Interpreting "Who's eaten?" as "Who is eaten?" is mostly for humorous purposes. However, I think you overstate the case for "Who is [past participle]?" not working, in theory. Especially since past participles do often function as adjectives, blurring the line between "Who is [adjective]?" and "Who has [past participle]?" You're right that modern colloquial speakers are more likely to use "has been" than "is" with a past participle, but that doesn't remove all ambiguity. Modern speakers understand "He's slain!" perfectly well.
    – LarsH
    Commented Jun 20, 2019 at 13:18
  • is vs. has with a past participle is also distinguished, for transitive verbs, by the presence of a separate direct object: In "He's slain!" vs. "He's slain it!", the mere presence/absence of it makes it quite clear that the first sentence contracts is and the second contracts has.
    – LarsH
    Commented Jun 20, 2019 at 13:22

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