English noun/Catalogs/English irregular nouns

The normal way to form a plural noun in English is to add the suffix -s, which changes into -es after an alveolar or postalveolar fricative, i.e. after s, z, ch and sh. Nouns with the stem ending in -ŷ replace this ending with -íes. But there are also many irregular nouns, some with English roots, others with plural forms from Latin, Greek, French, Italian and Hebrew. (The accents, which are not part of the language, are included to show stress and pronunciation: see English spellings for a table and English phonemes for the IPA. There is  also a key at the foot of this page. Words in italics suggest meaning, and an equals sign is placed between homophones.)

Nouns in -o that always change to -ôes in the plural are included in the table below; others are regular, ending in -ôs, while búffalo, càrgo, hâlo, mosquìto (-skì-), mótto, nô, tornâdo, volcâno and zêro can be seen with both -ôs and -ôes. Nouns of Latin origin in -us that always have -î in the plural are listed below, while cáctus, fôcus, fúngus, hippopótamus, óctopus and sýllabus can have both -î and -uses, though octopi is not correct Latin. Nouns of Greek origin in -sís (-ssíss), análysis, áxis, bâsis, crîsis, diagnôsis, émphasis, hypóthesis, neurôsis, oâsis, parénthesis, synópsis, sýnthesis and thêsis have their plurals in -sês (-ssêez): análysês (*ənáləssêez) etc.

Nouns of Latin origin in -ndum, addéndum, referéndum and memorándum, change to -nda: addénda, referénda (optionally), memoránda. Apart from vŏrtex, plural vŏrtices (-tíssêez), nouns of Latin origin in -ex and -íx (âpex, appéndix, cërvix, índex and mâtrix) have plurals in both -icês and -xes (-xíz). Indexes tend to be the things at the ends of books, indices the more mathematical meanings.

Invariable nouns
The following have the same form in the singular and plural: ãircraft, bárracks, bîson, cód, cróssroads, dêer animal (= dêar loved, expensive), dîce (dîe as the singular of dîce is archaic), físh  (although físhes can be used if more than one species of fish is involved), gállows, hálibut, héadquarters, mêans, moôse, óffspring, përch fish (otherwise përches), pîke fish (otherwise pîkes), sálmon (*sámmon), sêries, shêep, spêcies (-shíz), tròut and tûna.

Nouns with both regular and irregular forms
In the case of some nouns, there exist two plural forms—one regular ending in -s, the other irregular—where only one of the forms is correct in a given context:

anténna: anténnas radio, BrE anténnaê,  AmE anténnê insect

bròther: bròthers family, bréthren church

índéx: índéxes book, índícês ''mathematics

mêdium: mêdiums spiritualists, mêdia ''others

pénny: pénnies coins, pénce ''amount

përson: përsons formal, pêople everyday

Table of irregular nouns
Prefixed nouns are not included if their plural endings are the same as that of the root noun: for example the plural of snôwmán is snôwmén.