The plural of radius is radii.
As in "the radii is a straight line extending from the centre of a circle to the circumference"
There is no plural form for the word, countries. This word itself is a plural.
The plural of diary is diaries.
The plural form of the word gelato is gelati.
The plural form of the word 'deed' is 'deeds'.
The plural form of the word neurosis is "neuroses".
The plural of radius is radii
The plural form for the demonstrative pronoun this is these.
The plural form of the word inferno is infernos.
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.
There is no 'plural form' of the word 'minute'. The word is both singular and plural.