MB vs Britain

MB and Britain both are nouns.

Word	Noun	Adjective	Verb	Adverb
MB	Yes	No	No	No
Britain	Yes	No	No	No

MB (noun)	Britain (noun)
(a British degree) a bachelor's degree in medicine	a monarchy in northwestern Europe occupying most of the British Isles; divided into England and Scotland and Wales and Northern Ireland; `Great Britain' is often used loosely to refer to the United Kingdom
a unit of information equal to 1024 kibibytes or 2^20 (1,048,576) bytes
a unit of information equal to 1000 kilobytes or 10^6 (1,000,000) bytes