Some words are called Indefinite Pronouns, because   they refer to persons or things in a general way. They  are one, none, another, such, any, many, some, all, few, enough, both.

Also compounds of the above :- Anybody, anyone, anything; everybody, everyone, everything; nobody, no one, nothing; somebody, someone, something. 

Examples of use – I

One must do one’s best.

No one can tell what may happen.

One must be careful what one says. (Not: what he says.)

None in the family was taken ill (= not one).

None of the passengers was/were seasick. .

This pencil is blunt; please lend me another.

Others may say what they like; I don't care.

Such is not the case.

Any will do; any you like.

Will you have a cup of coffee?

Thanks, I am not allowed to have any.

Many were present, but none I knew.

Some prefer tennis to cricket.

Do have you any Afghan stamps?

Some, not many.

Are we all here now?

All is/are not required.

Very few were present at the meeting.

Do you have enough to do?

Both are to blame.

Examples of use – II

Has anybody (anyone) ever really seen a ghost?

You may have anything you need. I

Everybody (everyone) is talking about it with everybody else.

Is everything included in the account?

Who he is and where he goes, nobody cares and nobody knows.

Nothing was ever discovered about the way he died.

Somebody (someone) will have to answer for this.

Something will have to be done in this matter.

Note that else in the expression Somebody else (Someone else) is also an Indefinite Pronoun (somebody other).

Someone else must come and look after this child.

If I am not back in time, let somebody else take my place.

Of these Indefinite Pronouns a number are used as indefinite adjectives. They are : One, another, other, such, any, many, some, all, few, enough and both.

Examples of use.

One man may be as effective as a Committee.

Please give me another envelope.

Other people have holidays; why shouldn’t I?

Such conduct hardly gentlemanly.

Any kind of pen will do.

I have had many pets.

Some beggars are really deserving.

All snakes are not venomous.

I have seen few giraffes.

I hope they gave you enough bedclothes.

Both men were badly hurt.

Note the expression many a.

Many a man has failed where you succeeded (Many a man has = many men have).

I have toothache many and many a time (many and many a = very often).

Few = hardly any.

He has few friends

A few = some, but not many.

He has a few friends

Not a few = a good number.

Not a few such birds have been seen lately

Note that nouns are used with These (Few, A few and Not a few) Indefinite Adjectives are plural in form.

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