Irregular and special plurals
Nouns ending in –f or –fe usually have plurals ending in –ves.
The words dwarf, hoof, scarf and wharf can have two plural forms – one ending in –fs and another ending in –ves.
Dwarf – dwarfs/ dwarves
Hoof – hoofs / hooves
Scarf – scarfs / scarves
Other irregular plurals
The plural form pennies can be used to talk about separate penny coins. In an official style, persons is sometimes used as the plural of person. People, the plural form of the noun person, can be used as a singular noun when it means nation.
Plural same as singular
Some words ending in –s do not change in the plural. Common examples are given below.
Some singular uncountable nouns ending in –s do not have plural forms. Examples are: news, measles, billiards etc.
In modern English, data and dice are used as both singular and plural.
Nouns like aircraft, spacecraft, hovercraft etc do not change in the plural.