English: hilarities?

Tutoring English, a specific question arises: the tutor investigates if hilarity can pluralize to hilarities.

In my Feb 14 post I use the word hilarities, which the spell-checker doesn’t like, though it’s happy with hilarity. So, is the word hilarities valid?

A source online describes hilarity as “a situation of humour.” Well, then, two different situations of humour are two hilarities, aren’t they?

PS: The spell checker doesn’t like humour, either:)

Source:

dictionary.cambridge.org

Barber, Katherine et al. Oxford Canadian Dictionary of Current English. Don Mills: Oxford University Press, 2005.