fall-board vs protective cover

fall-board and protective cover both are nouns.

Word	Noun	Adjective	Verb	Adverb
fall-board	Yes	No	No	No
protective cover	Yes	No	No	No

As nouns, protective cover is a hypernym of fall-board; that is, protective cover is a word with a broader meaning than fall-board:

fall-board: the hinged protective covering that protects the keyboard of a piano when it is not being played
protective cover: a covering that is intend to protect from damage or injury

Other hypernyms of fall-board include protection, protective covering.

fall-board (noun)	protective cover (noun)
the hinged protective covering that protects the keyboard of a piano when it is not being played	a covering that is intend to protect from damage or injury