Plurals can be classified into two types; regular plurals, which are formed by inflecting the noun with the plural -s suffix, and irregular plurals which don't. The distinction between regular and irregular plurals is rather fuzzy.
- 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
A few words are used only in the plural. e.g. Clothes. These are uncountable, literally in the sense that we don't say "2 clothes, 3 clothes, 4 clothes", but do possess a grammatical number of "many" or "2". So are uncountable plurals.
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".