hospital bed vs single bed

hospital bed and single bed both are nouns.

Word	Noun	Adjective	Verb	Adverb
hospital bed	Yes	No	No	No
single bed	Yes	No	No	No

As nouns, single bed is a hypernym of hospital bed; that is, single bed is a word with a broader meaning than hospital bed:

hospital bed: a single bed with a frame in three sections so the head or middle or foot can be raised as required
single bed: a bed for one occupant

hospital bed (noun)	single bed (noun)
a single bed with a frame in three sections so the head or middle or foot can be raised as required	a bed for one occupant