What parts of speech is word sign?

Answer 1

sign is a noun -- The motel had a large blue neon sign.

sign is a verb -- We both signed the agreement. (past tense).

Answer 2

The word "sign" can function as both a noun and a verb. As a noun, it refers to a physical gesture or mark that conveys information. As a verb, it means to write one's name on a document or to communicate using gestures.