Most nouns form the plural by adding -s or -es.

Singular         Plural 
boat            boats 
hat              hats 
house          houses 
river             rivers

A noun ending in -y preceded by a consonant makes the plural with -ies.

Singular         Plural
a cry            cries 
a fly             flies 
a nappy       nappies 
a poppy       poppies 
a city           cities 
a lady          ladies 
a baby         babies

There are some irregular formations for noun plurals. Some of the most common ones are listed below.

Examples of irregular plurals:

Singular         Plural
woman         women 
man            men 
child            children 
tooth           teeth 
foot             feet 
person         people 
leaf              leaves 
half              halves 
knife            knives  
wife              wives  
life               lives  
loaf              loaves  
potato          potatoes 
cactus          cacti  
focus            foci  
fungus          fungi  
nucleus         nuclei  
syllabus        syllabi/syllabuses  
analysis        analyses  
diagnosis      diagnoses
oasis             oases 
thesis            theses  
crisis             crises 
phenomenon phenomena  
criterion         criteria  
datum           data

Some nouns have the same form in the singular and the plural.

Singular     Plural
sheep       sheep  
fish           fish  
species     species  
aircraft      aircraft

Some nouns have a plural form but take a singular verb.


news - The news is on at 6.30 p.m.
athletics - Athletics is good for young people.
linguistics - Linguistics is the study of language.
darts - Darts is a popular game in England.
billiards - Billiards is played all over the world.

Some nouns have a plural form and take a plural verb.


trousers - My trousers are too tight.
jeans - Her jeans are black.
glasses - Those glasses are his.

others include:

savings, thanks, steps, stair, customs, congratulations, tropics, wages, spectacles, outskirts, goods, wits