Irregular plural nouns
In English, there are nouns that don’t follow the standard rules for pluralization. There are no easy ways to remember them, so they generally have to be memorized.
Most singular nouns form the plural by adding -s.
     a sandwich - sandwiches
     a rose - roses
There are also irregular noun plurals. The most common ones are listed in the table below.
man - menfoot - feetmouse - mice
woman -womentooth - teethlouce - lice
child - childrengoose - geeseox - oxen
There are nouns that are used only in the singular (furniture, homework).
There are nouns that are used only in the plural (jeans, trousers, clothes, people).
There are also nouns that are used both in the singular and in the plural (sheep, deer).
Add -es to nouns ending in ch, sh, ss, z, x, o to make them plural.
For example:
words ending in -s:  gas — gases, bus — buses, lens — lenses
words ending in -x:  box — boxes, reflex — reflexes, hoax — hoaxes, tax — taxes
words ending in -sh: brush — brushes, wish — wishes, clash — clashes
words ending in -ch: lunch — lunches, watch — watches, punch — punches
words ending in -ss:  boss — bosses, kiss — kisses, business — businesses
If a noun ends with either -f or -fe, change these letters to a -v and add -es.
elf — elves
self — selves
knife — knives
loaf  — loaves
wolf — wolves
Drop the -y and add -es to the nouns ending with a consonant and y, change -y to -ies.
For example:

party — parties
lady — ladies
candy — candies