The English plural adds the usual "s" as "barnyards".
Barnyards is already plural. The singular form is barnyard.
It is a common noun but it is not plural.
There is no plural form for the word, countries. This word itself is a plural.
The plural form of the word "inferno" is "infernos."
There is no plural word for if.
The plural form is data.
There is no 'plural form' of the word 'minute'. The word is both singular and plural.
The plural of diary is diaries.
The plural form of the word gelato is gelati.
The plural form for the word 'pioneer' is pioneers.
The plural form of the word "baby" is "babies."
The plural form of the word 'deed' is 'deeds'.