The word 'nice' is not a noun. The word 'nice' is an adjective, a word used to describe a noun. The adjective 'nice' can describe a singular or a plural noun.
Examples:
This is a nice apple.
These are nice apples.
The word now means "good, pleasant, agreeable". It did not always mean that. Between 1700 and 1800 it meant "discerning, choice". Between 1500 and 1700 it had the sense of "requiring great precision or delicacy, a fine distinction." In the 1400s it meant "fussy, fastidious". Before that, in the 1300s, it meant a whole raft of nasty things, including "cowardly, immoral" in the later part of the century and "stupid and ignorant" in the early part of it. This insulting meaning comes from the Latin root of the word nescire which means "to know nothing".
Nice is an adjective, not a noun. It doesn't have a plural form.
The abstract noun form of the adjective 'nice' is niceness.
The noun 'mice' is the plural form of the singular noun 'mouse'.
The noun 'circus' is a singular noun.The plural noun is 'circuses'.
The noun juggler is a singular noun. The plural noun is jugglers.
Statistics is plural, the singular form is statistic.
The word moon is a singular noun. The plural noun is moons.
The noun 'mice' is the plural form of the singular noun 'mouse'.
"Children" is a plural noun. The singular form is "child."
The noun 'orange' is a singular noun, a word for one piece of fruit, a word for one color. The plural noun is oranges.Examples:Mom put an orange in my lunch box. (singular)The pumpkins were a nice shade of orange. (singular, one shade)I took a photo of the bowl of oranges. (plural)
The noun 'circus' is a singular noun.The plural noun is 'circuses'.
The word "loss" is singular. It refers to the act or instance of losing something.
The noun juggler is a singular noun. The plural noun is jugglers.
The singular noun is Tuesday.The plural noun is Tuesdays.
The singular noun is trio; the plural noun is trios.
The noun 'orchid' is a singular noun, a word for one.The plural noun is 'orchids'.
Statistics is plural, the singular form is statistic.
No, Mice is a plural noun. Mouse is the singular noun.
The word aisle is a singular noun. The plural noun is aisles.