Making Words Plural
5 rules
Basic Rules for Making Words Plural (-s and -es)
When a word ends in s, z, x, the soft 'ch,' or 'sh,' add -es to make it plural (fox→foxes, witness→witnesses, church→churches, quiz→quizzes). When a word ends in any other letter, add -s (affidavit→affidavits, machine→machines, trial→trials). When making a proper name plural, do not change the spelling of the name — just add -s or -es as appropriate (Mary→Marys, Wolf→Wolfs, Hess→Hesses, Perez→Perezes).
Plurals That Need Special Attention (Y, O, and F Endings)
Words ending in y: if a vowel precedes the y, add -s (attorney→attorneys, display→displays); if a consonant precedes the y, change y to i and add -es (company→companies, secretary→secretaries). Words ending in o: if the word relates to music, add -s only (soprano→sopranos, piano→pianos); if a consonant precedes the o, generally add -es (hero→heroes, tomato→tomatoes); if a vowel precedes the o, generally add -s (studio→studios, rodeo→rodeos). Words ending in f: some change f to v and add -es (half→halves, wife→wives); others just add -s (chef→chefs, plaintiff→plaintiffs, safe→safes). Some words use the same form for singular and plural (sheep, deer, fish, moose).
Irregular Plurals: Internal Vowel Change and -en Endings
Some words form their plural by changing an internal vowel (mouse→mice, man→men, woman→women, foot→feet, tooth→teeth, louse→lice, goose→geese). Some words add -en for the plural (ox→oxen, child→children). These are irregular forms that must be known — no general rule predicts them.
Plurals of Foreign (Latin) Words Adopted into English
Some foreign words, particularly those from Latin, have retained the plural of the original language. The plural form is usually based on the last letters of the singular: -is becomes -es (basis→bases, analysis→analyses, oasis→oases); -um becomes -a (curriculum→curricula, addendum→addenda, memorandum→memoranda); -us becomes -i (alumnus→alumni, cactus→cacti, nucleus→nuclei); -a becomes -ae (vertebra→vertebrae, alumna→alumnae, bursa→bursae); -on becomes -a (criterion→criteria, phenomenon→phenomena); -ex or -ix becomes -ices (appendix→appendices or appendixes, index→indices or indexes).
Plurals of Compound Words (Solid, Hyphenated, and Multi-Word)
Compound words can be solid, hyphenated, or multiple words — there is no way to determine which form is correct except by looking up the word in the dictionary. For solid compound nouns, add the plural to the end of the word (roommate→roommates, bookkeeper→bookkeepers). Exception: the only solid word where the plural is inserted in the middle is passerby→passersby. For hyphenated or multi-word compound nouns that contain a main noun, make the main noun plural (editor in chief→editors in chief, brother-in-law→brothers-in-law, cross-section→cross-sections). For hyphenated or multi-word compound nouns with no main noun, add the plural to the end (go-between→go-betweens, look-alike→look-alikes, know-it-all→know-it-alls).