INDEFINITES
A Introduction
Look at these examples.
Everyone enjoyed the show. It was a great success.
The police searched the house but found nothing.
Let's find somewhere to eat.
Nobody came into the shop all afternoon.
With every, some and no, we can form words ending in one, body, thing and where.
everyone!everybody = all the people everything = all the things everywhere = (in) all the placessomeone/somebody = a person something = a thing somewhere — (in) a place
no one/nobody = no person nothing = no things nowhere = (in) no places

Words ending in thing can also mean actions or ideas.
Something awful has happened. You must tell me everything.

B Someone and anyone, etc
We can also form words with any: anyone, anybody, anything, anywhere.

Positive: There's someone in the phone box.
Negative: I looked round the shops, but I didn't buy anything.
Question: Has anyone seen today's newspaper?
Offer/Request: Could you do something for me, please?
C Singular and plural
We use a singular verb after everyone, something, anything, etc.

Everywhere was very crowded. No one knows how to start the motor.
After words with one or body, we normally use they/them/their, even though the verb is singular.
Everyone is having their lunch. Nobody wants to have their coffee yet.