Is tropical a common noun

The noun 'tropics' is a common noun, a general Word for any area located between the Tropic of Cancer and the Tropic of Capricorn.

A common noun is capitalized only when it is the first Word in a sentence.

The noun 'tropics' is an uncountable noun, a type of aggregate noun, a Word for any number of elements or areas of this region.

The nouns 'Tropic of Cancer' and 'Tropic of Capricorn' are proper nouns, the names of specific geographic features.