A pronoun
is a substitute for a noun. It refers to a person, place, thing, feeling or
quality, but does not refer to it by its name.
An antecedent
is the word, phrase or clause to which a pronoun refers.
Pronouns
such as anybody, everyone, someone,
somebody, no one
and nobody are always singular.
Either
and neither are always
singular.
Pronouns must agree with their antecedents in gender (male or female) as well as number.
Don’t
use “their” (plural) in place of “his or her” (singular). If it’s
awkward, reconstruct the sentence.