chess opening vs chess

chess opening and chess both are nouns.

Word	Noun	Adjective	Verb	Adverb
chess opening	Yes	No	No	No
chess	Yes	No	No	No

chess opening (noun)	chess (noun)
a recognized sequence of moves at the beginning of a game of chess	a board game for two players who move their 16 pieces according to specific rules; the object is to checkmate the opponent's king
	weedy annual native to Europe but widely distributed as a weed especially in wheat