- we usually add -s:
- pronounced /s/: book - books; night - nights;
- pronounced /z/: friend - friends; eye - eyes;
- -es (pronounced /ɪz/) to words ending in -ch/-x/-s/-sh: watch - watches; box - boxes; glass - glasses; dish - dishes;
- -ies to words ending -y: cherry - cherries; sky - skies;
- Words ending in -o
- Add -es: hero - heroes; potato - potatoes; tomato - tomatoes;
- Add -s: piano - pianos; radio - radios; video - videos;
For historical reasons a few plurals are irregular.
- Plural the same as the singular. Usually animals - fish, sheep, swine, deer; also series
- Ending in -ves for some words ending –f/fe: half - halves; knife - knives; life - lives; loaf - loaves; shelf - shelves; wife - wives; but note the following: beliefs, chiefs, gulfs, proofs, roofs (/ru:vz/). The plural of dwarf can be dwarfs (/dwɔːrfs/) or dwarves (/dwɔːrvs/).
- Some words ending in /θ/ have both a regular /θs/ and an irregular /ðz/ plural: baths /bæθs,AmE bæðz,AmE  bɑːðzBrE / - oaths - paths - truths - wreaths - youths
- There is a people set, consisting of child – children /tʃaɪld - ˈtʃɪldrən/; person - people; man – men; woman - women /ˈwʊmən - ˈwɪmɪn/;
- There is an animal set, consisting of goose - geese /ɡuːs - ɡiːs/; louse - lice; mouse - mice; ox - oxen;
- There is a body parts set:foot - feet /fʊt - fiːt/; tooth – teeth;
- there are miscellaneous others, e.g. house - houses /ˈhaʊs - ˈhaʊzɪz/;
- Plural is different only in written form: chairman - chairmen /ˈtʃeərmən/; milkman - milkmen /ˈmɪlkmən/; postman - postmen /ˈpəʊstmən/
- Singular and plural are spelled identically, but have a different pronunciation: corps /kɔːr, kɔːrz/
- Loanword plurals:
- French plurals: chateau - chateaux.
- Latin plurals: datum - data,
- Greek plurals: analysis - analyses /əˈnæləsɪs - əˈnæləsiːz/; basis - bases /ˈbeɪsɪs - ˈbeɪsiːz/; crisis - crises /ˈkraɪsɪs - ˈkraɪsiːz/
- process - processes: This word has a regular plural and irregular ones.
- American English: /ˈprɒses - ˈprɒsesɪz, ˈprɒsəsɪz, ˈprɒsəˌsiːz/;
- Received Pronunciation: /ˈprəʊses - ˈprəʊsesɪz, ˈprəʊsəsɪz/
- axes /ˈæksɪz/ plural of axAmE/axeBrE; /ˈæksiːz/ plural of axis
- bases /ˈbeɪsɪz/ plural of base; /ˈbeɪsiːz/ plural of basis
Some nouns ending in -s are mass nouns: measles – a news item – mathematics - physics – politics
Words used only in the plural
A few words are used only in the plural. e.g. Clothes.
Words usually used in the plural
Words referring to a pair of something are usually plural, e.g. trousers. But can sometimes be used in the singular, e.g. "a trouser leg".
- Random House Dictionary, process. Recent years have seen the increasing popularity of an [-eez] pronunciation for processes, perhaps by mistaken analogy with such plurals as theses and hypotheses, with which it has no connection. Although this newer pronunciation is increasingly common, it is regarded by some educated speakers as an affectation.