Is lucky a common or proper noun?

Answer 1

The word 'Lucky' (capital L) is a noun, a proper noun; a common name for a pet or the nickname of a person.

The word 'lucky' (lower case l) is an adjective, a word used to describe a noun (a lucky penny, a luckybreak, a lucky guess, etc.)

Answer 2

The word 'lucky' (lower case l) is NOT a noun.

The word 'lucky' is an adjective, a word used to describe a noun (a lucky penny, a lucky break, a luckyguess, etc.)

The word 'Lucky' (capital L) is a proper noun as a name for a pet or the nickname of a person.

The noun form of the adjective 'lucky' is luckiness.
The word 'lucky' is the adjective form of the noun luck.