There is no plural form for the word, countries. This word itself is a plural.
The plural form for the noun navy is navies; the plural possessive form is navies'.
The plural form of the word "inferno" is "infernos."
There is no plural word for if.
The plural form is data.
In Chinese, the plural form of the word "minute" is "分钟" (fēnzhōng).
The plural of diary is diaries.
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'.
The plural form of the word signal is signals.
The plural form of the word gelato is gelati.