b b /ˈbiː/

noun

1. (physics) a unit of nuclear cross section; the effective circular area that one particle presents to another as a target for an encounter  ( b , barn )
   (physics) a unit of nuclear cross section; the effective circular area that one particle presents to another as a target for an encounter
   

 B

1. () Aerobic rod-shaped spore-producing bacterium; often occurring in chainlike formations; found primarily in soil  ( bacillus , B )
   aerobic rod-shaped spore-producing bacterium; often occurring in chainlike formations; found primarily in soil
    Soil samples often contain B bacterium, which is rod-shaped and spore-producing.
   Soil samples often contain B bacterium, which is rod-shaped and spore-producing.
   
   
2. The blood group whose red cells carry the B antigen  ( B , group B , type B )
   the blood group whose red cells carry the B antigen
   
3. The 2nd letter of the Roman alphabet  ( B )
   the 2nd letter of the Roman alphabet
   
4. A logarithmic unit of sound intensity equal to 10 decibels  ( B , Bel )
   a logarithmic unit of sound intensity equal to 10 decibels
   
5. A trivalent metalloid element; occurs both in a hard black crystal and in the form of a yellow or brown powder  ( atomic number 5 , B , boron )
   a trivalent metalloid element; occurs both in a hard black crystal and in the form of a yellow or brown powder
   
   
6. Originally thought to be a single vitamin but now separated into several B vitamins  ( B , B complex , B-complex vitamin , B vitamin , vitamin B , vitamin B complex )
   originally thought to be a single vitamin but now separated into several B vitamins