Everyone is not a singular pronoun. It is an indefinite pronoun that is treated as singular. Indefinite pronouns refer to people, places, objects, or things without pointing to a specific one. But because it is indefinite, making sentences agree in number is sometimes complicated.

Here is an example of such a difficult sentence:

Wrong: Everyone have gone their separate ways.

Less Wrong: Everyone has gone his separate way.

Less Wrong: Everyone has gone their separate way.

Least Wrong: Everyone has gone their separate ways.

Right but too clumsy: Everyone has gone his or her separate way.

Indefinite Pronoun Rules:

Indefinite pronouns, like collective nouns, can be singular or plural, depending on how they are used in a sentence. Singular indefinite pronouns take a singular verb; plural indefinite pronouns take a plural verb. Here are some guidelines to follow:

● Indefinite pronouns that end in -one are always singular. These words include anyone, everyone, someone, and one.

● Indefinite pronouns that end in -body are always singular. These words include anybody, somebody, nobody.

● The indefinite pronouns both, few, many, others, and several are always plural.

● The indefinite pronouns all, any, more, most, none, and some can be singular or plural, depending on how they are used.