1. Usually add s:
- pad - pads
- wave - waves
2. If the word ends in O, usually ad es:
- mango - mangoes
- tomato - tomatoes
3. If the word ends in S, X, Z, CH, or SH, add es:
- mass - masses
- tax - taxes
- clash - clashes
- buzz - buzzes
- touch - touches
4. If the word ends in Y and there's a vowel (a,e,i,o,u) before the Y, add s:
- key - keys
- way - ways
5. If the word ends in Y and there's a consonant before the Y, change the y to i and add es:
- butterfly - butterflies
- injury - injuries
6. If a proper noun (someone's name) ends in Y, just add s:
- the McKinley family - the McKinleys
- the Henley family - the Henleys
7. If a compound noun (a noun containing more than one word) has a main noun in it, add the s to the main noun:
- one mother-in-law, two mothers-in-law
- one certificate of employment, two certificates of employment
8. If a compound noun has no main noun in it, add the s at the end:
- one follow-up, two follow-ups
- one trade-in, two trade-ins
Looks easy so far, right?
Not so fast...
9. There are some nouns that stay the same whether you refer to the singular or plural form:
- moose - moose
- deer - deer
- species - species
- sheep - sheep
- series - series
- swine - swine
12. Other nouns are based on rules from foreign languages :
- basis - bases
- crisis - crises
- criterion - criteria
- nucleus - nuclei
- stimulus - stimuli
- datum - data
13. There are other nouns which do not follow the above rules :
- mouse - mice
- banjo - banjos
- passerby - passersby
- ox - oxen
- knife - knives
- foot - feet
- child - children
14. Just to be sure, consult your dictionary to determine the correct plural form for each word.
Attribution to Rebecca Elliot and her book Painless Grammar (c) 2006, 1997
Other noun tips:
16 Tips on How to Capitalize Nouns (Nouns, Part 1 of 3)
9 Tips about Possessive Nouns (Nouns, Part 2 of 3)
14 Tips on Making Plural Nouns (Nouns, Part 3 of 3)
