bits per inch vs density

bits per inch and density both are nouns.

Word	Noun	Adjective	Verb	Adverb
bits per inch	Yes	No	No	No
density	Yes	No	No	No

As nouns, density is a hypernym of bits per inch; that is, density is a word with a broader meaning than bits per inch:

bits per inch: a measure of how densely information is packed on a storage medium
density: the amount per unit size

Other hypernyms of bits per inch include denseness.

bits per inch (noun)	density (noun)
a measure of how densely information is packed on a storage medium	the amount per unit size
	the spatial property of being crowded together