Plural of convex; multiple convex surfaces or shapes.
Convex (the noun form, meaning a convex surface) + -es (regular plural). 'Convex' can function as a noun in technical contexts, making 'convexes' a valid plural form.
In geometry and optics, you might hear 'convexes and concaves' when discussing lens shapes, where both terms become nouns representing types of surfaces. This is specialized technical usage that most people never encounter.
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