bpi vs bits per inch

bpi and bits per inch both are nouns.

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

As nouns, bpi and bits per inch are synonyms defined as:

bpi and bits per inch: a measure of how densely information is packed on a storage medium

bpi (noun)	bits per inch (noun)
a measure of how densely information is packed on a storage medium	a measure of how densely information is packed on a storage medium