Nouns that have no plural form are called mass nouns, uncountable nouns, or non-count nouns.
The plural form for the demonstrative pronoun this is these.
The plural form of the word inferno is infernos.
There is no plural form of this noun. It is the name of a single, unique area of study (science). No plural form is necessary. Alternatively, "physics" is already the plural form of the word "physic", a now-archaic word meaning "medicine".
The plural form is ranches.
There is no plural word for if.
There is no plural form for the word, countries. This word itself is a plural.
The plural form is data.
The plural form of the word "baby" is "babies."
The plural form for the word 'pioneer' is pioneers.
The plural form of the word "pharynx" is "pharynges."
The plural form of vow is vows.
The plural form of the noun 'march' is marches.Nouns ending in ch, sh, s, x, and z add -es to the end of the word to form the plural.