PRONOUNS
Definitions to know:
PRONOUN--a pronoun is a word that takes the place of a noun or another pronoun
ANTECEDENT--an antecedent is the word(s) a pronoun replaces

Example: Billy lost his cell phone today.

INDEDFINITE PRONOUN--an indefinite pronoun is a pronoun whose antecedent is not certain
There are plenty of words that are indefinite pronouns, but these three are always singular:
Everybody, everyone, everything
Pronouns are our FRIENDS!  

Friends help each other out, and pronouns help us do these two things:
Condense our writing
Add variety to our language
antecedent
pronoun
Some Lists for Reference:
All of these do NOT have
to be memorized!  This
is just a reference.