Notice that words are characterized as nouns by their ability to form plurals. (Some pronouns have this ability as well, e.g., other and others.) You will form the plural for most nouns by adding ‑s or ‑es.
Just Add ‑s
Plurals of Nouns by Adding -s
Consider these plurals formed by the “just add -s” rule:
Many people violate the “just add ‑s” rule, often by using an “apostrophe ‑s” to form the plural. You should use the apostrophe only when you must avoid an ambiguity. Here are some examples of the “just add ‑s” rule in action:
Proper names, just add -s.
The tribe had three Igors and two Ambers.
Capital letters, just add -s, unless the result would be ambiguous.
She writes her Ns in a strange way.
But: She writes her I’s in a strange way.
Lowercase letters, use the apostrophe.
Mind your p’s and q’s.
Italicized videotape or book, just add -s and don’t italicize the ‑s.
The video store ordered six Titanics.
Decades or other numbers, just add ‑s.
She was stuck in the 1960s.
Acronyms or abbreviations, just add ‑s
(if periods do not appear)
The young couple set up two IRAs.
But: He roomed with two M.D.’s.
Words referred to as words, italicize the word and add a nonitalicized -s.
He used too many howevers in his style.
If you violate the “just add -s” rule and use the apostrophe, you need to study the apostrophe. Simply download the eBook Rules on Punctuation.
Just Add ‑es
Making Nouns Plural with -es
If you don’t add an -s to form the plural of a noun, chances are you’ll add ‑es. Consider the “just add ‑es” rule:
Nouns ending in a consonant and a ‑y, change ‑y to ‑i and add ‑es.
But proper names ending in a consonant and a ‑y, just add ‑s.
But nouns ending in a vowel and a ‑y, just add ‑s.
Nouns ending in ‑s, ‑ss, ‑ce, ‑sh, ‑ch, ‑tch, ‑ge, ‑dge, ‑x, and ‑ze, just add ‑es. These endings are called sibilants.
Some nouns ending in a consonant and an ‑o, just add ‑es.
But for some, add either ‑es or ‑s.
|banjo||banjoes or banjos|
|cargo||cargoes or cargos|
And for some, add only ‑s.
And for those ending in a vowel and an ‑o, just add ‑s.
Do Something Else
Making Nouns Plural Some Other Way
Then we have a fairly long list of words that form their plurals in varying ways. Everyone knows that the plural of child is children, the plural of foot is feet, the plural of woman is women, and man-men, and louse-lice. And so on. Some people get all agitated when they see the plural of memorandum formed by adding ‑s: memorandums. But a quick check of a reputable dictionary reveals that memorandums is perfectly acceptable. Random House, p. 1199.
So for words like fungus, passer-by, man-of-war, vertex, and others, I’ll simply punt and suggest that you (1) check the dictionary (use Dictionary.com) and (2) be aware of your audience and adhere to its preferred style.
You may download our entire discussion of the Parts of Speech. Simply download the Grammar eBook Understanding the Parts of Speech.