In simplest terms plural means "more than one."
To show that a noun is plural, we normally add an -s or -es to the word.
Example: one dog, two dogsSometimes the spelling rule requires that the consonant be doubled before adding the -es.
one bus two buses
Example: one quiz, two quizzes
There are a few irregular plurals such as men, children, women, oxen, and a number of words taken directly from foreign languages such as alumni (plural of alumnus) or media (plural of medium).
We also speak of the plural form of pronouns--that is, pronouns that take the place of plural nouns like we, you, and they.
We also speak of the plural form of verbs--that is, verbs that go with a plural subject. In English this is significant only in the present tense and the past tense of the verb to be.
For example, the third person plural past tense of the verb to be is we were.
For the formation of the plural of letters, symbols, and words as words, see Apostrophes with Plurals of Underlined Items.