Guide to English grammar

What do you do in your spare time?
What sport do you play?
Which is the best route?
Which way do we go now?
We use what when there is an indefinite (and often large) number of possible answers. We use which when there is a definite (and often small) number of possible answers. What relates to the indefinite word a, and which to the definite
word the.
What sport...? (a sport)
(Tennis, or golf, or football, or...)
Which way...? (one of the ways)
(Right or left?)
The choice of what or which depends on how the speaker sees the number of possible answers. In some contexts either word is possible.
What newspaper/Which newspaper do you read?
What parts/Which parts of France have you visited?
What size/Which size do you take?

NOTE
We can use what to suggest that there are no possible answers.

Why don't you invite a few friends? -What friends? I haven't got any friends.

3 Who and whom

When who is the object, we can use whom instead.
Who/Whom did you invite?
Whom is formal and rather old-fashioned. Who is more common in everyday speech.
When who/whom is the object of a preposition, there are two possible patterns. The pattern with whom is formal.
Who were you talking to?
To whom were you talking?

A practical guide to English grammar 28

4 How
1 How can express means or manner.
How do you open this bottle? (You open this bottle somehow.)
How did the children behave? (The children behaved well/badly.)

2 When it expresses degree, how can come before an adjective or adverb.
How wide is the river? (20/30 metres (GB)/meters (US) wide?)
How soon can you let me know? (very soon/quite soon?)

For question phrases with how, • 28.

3 We also use how as an adjective or adverb in friendly enquiries about someone's well-being, enjoyment or progress.