Number refers to singular (one) and plural (more than one).
There are some irregular noun in its plurals form. Here is a list of some of most common nouns you should know.
| SINGULAR | PLURAL |
| woman | women |
| man | men |
| child | children |
| tooth | teeth |
| foot | feet |
| person | people |
| mouse | mice |
| goose | geese |
| 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 |
| sheep | sheep |
| fish | fish |
| deer | deer |
| species | species |
| aircraft | aircraft |
Some nouns have a plural form but take a singular verb.
| Plural Nouns with singular verb | Sentence |
| news | The news is 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 fixed plural form and take a plural verb. They are not used in the singular, or they have a different meaning in the singular.
Examples: trousers, jeans, glasses, savings, thanks, steps, stairs, customs, congratulations, tropics, wages, spectacles, outskirts, goods, wits
| Plural noun with plural verb | Sentence |
| trousers | My trousers are too tight. |
| jeans | Her jeans are black. |
| glasses | Those glasses are his. |
A few nouns have two plurals differing in meaning.
brother —brothers (by blood), brethren (of a society or church).
cloth —cloths (kinds of cloth), clothes (garments).
die —dies (stamps for coins, etc.), dice (for gaming).
fish —fish (collectively), fishes (individuals or kinds).
genius —geniuses (men of genius), genii (spirits).
index —indexes (to books), indices (signs in algebra).
pea —peas (separately), pease (collectively).
penny—pennies (separately), pence (collectively).
shot —shot (collective balls), shots (number of times fired).
In speaking of coins, twopence, sixpence, etc., may add -s, making a double plural, as two sixpences.