what

Which, especially which of an open-ended set of possibilities.

What colour are you going to use?

What time is it?

Which.

I wonder what colour he is going to use.

I know what colour I am going to use.

Any ... that; all ... that; whatever.

He seems to have lost what sense he had.

What money I earn is soon spent.

Emphasises that something is noteworthy or remarkable in quality or degree, in either a good or bad way; may be used in combination with certain other determiners, especially 'a', less often 'some'.

This shows what beauty there is in nature.

You know what nonsense she talks.

Emphasises that something is noteworthy or remarkable in quality or degree, in either a good or bad way; may be used in combination with certain other determiners, especially 'a', less often 'some'.

What nonsense!

Wow! What a speech.

Which thing, event, circumstance, etc.: used in asking for the specification of an identity, quantity, quality, etc.

Hammer in that nail —What with? I didn't bring my set of tools.

What is your name?

That which; those that; the thing(s) that.

He knows what he wants and what to do to get it.

What is amazing is his boundless energy.

Anything that; all that; whatever.

I will do what I can to help you.

What I'll do is, I'll phone you to let you know.

That; which; who.

Look! It's that bloke again what was 'ere yesterday!

"I'll tell it ye from the beginning," he said. "My time is from ten at night to six in the morning. At eleven there was a fight at the 'White Hart'; but bar that all was quiet enough on the beat. At one o'clock it began to rain, and I met Harry Murcher—him who has the Holland Grove beat—and we stood together at the corner of Henrietta Street a-talkin'. Presently—maybe about two or a little after—I thought I would take a look round and see that all was right down the Brixton Road. It was precious dirty and lonely. Not a soul did I meet all the way down, though a cab or two went past me. I was a strollin' down, thinkin' between ourselves how uncommon handy a four of gin hot would be, when suddenly the glint of a light caught my eye in the window of that same house. Now, I knew that them two houses in Lauriston Gardens was empty on account of him that owns them who won't have the drains seen to, though the very last tenant what lived in one of them died o' typhoid fever. I was knocked all in a heap therefore at seeing a light in the window, and I suspected as something was wrong. When I got to the door——"

In what way; to what extent.

What does it matter?

What do you care?

Used before a prepositional phrase to emphasise that something is taken into consideration as a cause or reason; usually used in combination with 'with' (see what with), and much less commonly with other prepositions.

In short; what by the indiscretion of people here, what by the rebound which came often back from London, what by the private interests and ambitious views of persons in the French court, and what by other causes unnecessary to be examined now, the most private transactions came to light [...]

The Chinese of all ranks, and in every place, received my books gladly, and listened with patience to what I had to say about the true God.—So that what from opportunities of attending to the object of my Mission among the Chinese—what from seasons of religious instruction to Dutch and English—what from intercourse with gentlemen of education and knowledge of the world—what from occasions of stating clearly the object of Missions, and of endeavouring to remove prejudices against them—and what from the view of a highly cultivated country, happy under an enlightened and liberal government, I have much reason to be satisfied with this journey …