What

As an interrogative pronoun, used in asking questions regarding either persons or things; as, what is this? what did you say? what poem is this? what child is lost?

As an exclamatory word: -- (a) Used absolutely or independently; -- often with a question following.

Used adjectively, meaning how remarkable, or how great; as, what folly! what eloquence! what courage!

Sometimes prefixed to adjectives in an adverbial sense, as nearly equivalent to how; as, what happy boys!

As a relative pronoun

Used substantively with the antecedent suppressed, equivalent to that which, or those [persons] who, or those [things] which; -- called a compound relative.

Used adjectively, equivalent to the . . . which; the sort or kind of . . . which; rarely, the . . . on, or at, which.

Used adverbially in a sense corresponding to the adjectival use; as, he picked what good fruit he saw.

Whatever; whatsoever; what thing soever; -- used indefinitely.

Used adverbially, in part; partly; somewhat; -- with a following preposition, especially, with, and commonly with repetition.

Something; thing; stuff.

Why? For what purpose? On what account?