What Definition

wŏt, wŭt, hwŏt, hwŭt; wət, hwət when unstressed

pronoun

Which thing or which particular one of many.

What are you having for dinner? What did she say?

American Heritage

The nature, class, name, purpose, etc. of a thing.

What is that object? what is your address?

Webster's New World

An explanation or repetition of something previously said.

You told them what?

Webster's New World

Which kind, character, or designation.

What are these objects?

American Heritage

Such an explanation or repetition.

“Sh. Quiet!” “What?”

Webster's New World

Synonyms:

Synonyms:
and-more
and other things too numerous to mention
etcetera
and-so-forth
/etc
that which
anything
something
whichever
whatever
everything
anything at all
which? what sort? what kind? what thing? what means?

adjective

Which or which kind of.

What man told you that? he knows what role she played.

Webster's New World

As much, or as many, as.

Take what time (or men) you need.

Webster's New World

Whatever.

They soon repaired what damage had been done.

American Heritage

How great, surprising, magnificent, disappointing, etc.

What a man! what nonsense!

Webster's New World

adverb

How much; in what respect; how.

What does it matter?

American Heritage

In what respect? to what degree? how?

What does it matter?

Webster's New World

How greatly, surprisingly, etc.

What tragic news!

Webster's New World

Why?

Webster's New World

In some manner or degree; in part; partly; usually followed by with.

What with singing and joking, the time passed quickly.

Wiktionary

conjuntion

That.

I don't know but what I'll go.

American Heritage

So far as; as much as.

We warned them what we could.

Webster's New World

interjection

Used to express surprise, anger, confusion, etc.

What! no dinner?

Webster's New World

Used as a tag question, often to solicit agreement.

American Heritage

(UK, colloquial, dated) Is that not true?

It's a nice day, what? (sometimes repeated, e.g.: What-what?)

Wiktionary

noun

The true or basic quality of something.

To uncover the what and why of their relationship.

Webster's New World

determiner

Which; which kind of.

What shirt are you going to wear?

What time is it?

What kind of car is that?

Wiktionary

How much; how great (used in an exclamation).

What talent he has!

What a talent!

Wiktionary

Other Word Forms of What

Noun

Singular:

what

Plural:

whats

Idioms, Phrasal Verbs Related to What

Origin of What

From Middle English what, from Old English hwæt (“what"), from Proto-Germanic *hwat (“what"), from Proto-Indo-European *kʷód (“what"), neuter form of *kʷós (“who"). Cognate with Scots what (“what"), North Frisian wat (“what"), Saterland Frisian wat (“what"), West Frisian wat (“what"), Dutch wat (“what"), Low German wat (“what"), German was (“what"), Danish hvad (“what"), Swedish vad (“what"), Icelandic hvað (“what"), Latin quod (“what, which").

From Wiktionary
Middle English from Old English hwæt kwo- in Indo-European roots

From American Heritage Dictionary of the English Language, 5th Edition