B vs b

B and b both are nouns.

Word	Noun	Adjective	Verb	Adverb
B	Yes	No	No	No
b	Yes	No	No	No

As nouns, B and b are synonyms defined as:

B (noun)	b (noun)
aerobic rod-shaped spore-producing bacterium; often occurring in chainlike formations; found primarily in soil	the 2nd letter of the Roman alphabet
the blood group whose red cells carry the B antigen	(physics) a unit of nuclear cross section; the effective circular area that one particle presents to another as a target for an encounter
the 2nd letter of the Roman alphabet
a logarithmic unit of sound intensity equal to 10 decibels
a trivalent metalloid element; occurs both in a hard black crystal and in the form of a yellow or brown powder
originally thought to be a single vitamin but now separated into several B vitamins