Someone, somebody, something, somewhere are indefinite pronouns. They function in a similar way to some. We use them in affirmative clauses and in questions expecting a particular answer. We can use them to refer to both general and specific people or things. We use them with a singular verb:

I know someone who gives piano lessons. (a specific person)

Somebody has obviously made a mistake. (general, we don’t know who)

Can you hear something?

There was no mistaking the smell. Burning. There was a fire somewhere.

We often use the plural pronoun they to refer back to (singular) someone or somebody when we do not know if the person is male or female:

Never judge someone by the way they look. (or Never judge someone by the way he or she looks.)

See also:

One

Sexist language

Someone and somebody have no difference in meaning. Somebody is a little less formal than someone. Someone is used more in writing than somebody. Somebody is more common in speaking:

We can no longer assume that because someone can do the job, they can teach the skill.

Somebody’s got to say something to her. She can’t behave like that.

We can use both something and anything in negative questions. They have different meanings:

Didn’t she bring something to eat? (I think she did bring something.)

Didn’t she bring anything to eat? (I’m surprised she didn’t bring something.)

See also:

Anyone, anybody or anything?

Some

Pronouns: indefinite (-body, -one, -thing, -where)