hard disc vs magnetic disk

hard disc and magnetic disk both are nouns.

Word	Noun	Adjective	Verb	Adverb
hard disc	Yes	No	No	No
magnetic disk	Yes	No	No	No

As nouns, magnetic disk is a hypernym of hard disc; that is, magnetic disk is a word with a broader meaning than hard disc:

hard disc: a rigid magnetic disk mounted permanently in a drive unit
magnetic disk: (computer science) a memory device consisting of a flat disk covered with a magnetic coating on which information is stored

Other hypernyms of hard disc include disc, disk, magnetic disc.

hard disc (noun)	magnetic disk (noun)
a rigid magnetic disk mounted permanently in a drive unit	(computer science) a memory device consisting of a flat disk covered with a magnetic coating on which information is stored