everyone, everybody, everything
someone, somebody, something
anyone, anybody, anything
no one, nobody, nothing
In statement sentences, everyone, everybody, someone, somebody, no one, nobody are always considered as singular (he or she); therefore, they take singular verb.
• Somebody has stolen his car.
• No one was late to class.
• Has everyone handed in the paper?
In question tags, those indefinite pronouns are considered as plural: they.
• Everyone should use computer for their work, shouldn’t they?
• No one needs any help, do they?
• Nobody wants to believe his words, do they?
• Somebody left his book on the desk.
• Everyone has his own ideas.
A singular personal pronoun is used in formal English to refer to an indefinite pronoun.
• Somebody left their book on the desk.
• Everybody has their own ideas.
In spoken English, a plural personal pronouns is often used to refer to an indefinite pronoun.