WordNet sense 1 (originally thought to be a single vitamin but now separated into several B vitamins):

B-complex vitamin, B complex, B vitamin, vitamin B, vitamin B complex

WordNet sense 2 (a trivalent metalloid element; occurs both in a hard black crystal and in the form of a yellow or brown powder):

boron

WordNet sense 3 (a logarithmic unit of sound intensity equal to 10 decibels):

bel

WordNet sense 4 ((physics) a unit of nuclear cross section; the effective circular area that one particle presents to another as a target for an encounter):

barn

WordNet sense 5 (the 2nd letter of the Roman alphabet):

letter b

WordNet sense 6 (the blood group whose red cells carry the B antigen):

group B, type B

WordNet sense 7 (aerobic rod-shaped spore-producing bacterium; often occurring in chainlike formations; found primarily in soil):

bacillus