Pb vs computer memory unit

Pb and computer memory unit both are nouns.

Word	Noun	Adjective	Verb	Adverb
Pb	Yes	No	No	No
computer memory unit	Yes	No	No	No

As nouns, computer memory unit is a hypernym of Pb; that is, computer memory unit is a word with a broader meaning than Pb:

Pb (noun)	computer memory unit (noun)
a unit of information equal to 1000 terabits or 10^15 bits	a unit for measuring computer memory
a soft heavy toxic malleable metallic element; bluish white when freshly cut but tarnishes readily to dull grey