There is no plural form. If used as a noun. I see one sudanese I see one hundred sudanese. If used adjectivally. I see one sudanese man I see one hundred sudanese men.
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.
In Chinese, the plural form of the word "minute" is "分钟" (fēnzhōng).
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'.
The plural form of the word signal is signals.
The plural form of the word "search" is "searches".