where's

One spelling, four possible verbs. Here the 's is the copula is, fused with where in a form typical of speech and informal writing. A noun phrase follows it directly (where's your hat, where's the station), and the singular verb expects a singular subject. The same letters can also stand for the "has" contraction or the colloquial "does" form. The word after the subject usually shows which one is meant.

Here the 's is the auxiliary has, so a past participle follows the subject: where's she gone, where's the time gone. That participle is the quickest way to tell it from the is reading. Where's she going takes is, while where's she gone takes has. When the contraction could be misread, the full where has is always available.

A casual-speech reduction in which 's stands for does, so the verb after the subject appears in its bare form: where's he go every day, where's this train go. That bare verb is the giveaway, because with is the same sentence would need going. In writing, and in any careful register, the full where does is the safer choice.

Number agreement breaks down here: the singular-looking 's stands in for plural are before a plural subject, as in where's my glasses or where's them papers what I give you. It turns up in casual speech, often alongside other nonstandard grammar, but edited prose keeps where are. Learners should recognize it rather than imitate it.