kb vs Mb

kb and Mb both are nouns.

Word	Noun	Adjective	Verb	Adverb
kb	Yes	No	No	No
Mb	Yes	No	No	No

kb (noun)	Mb (noun)
a unit of information equal to 1000 bits	a unit of information equal to 1000 kilobits or 10^6 (1,000,000) bits