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.