Bn. aerobic rod-shaped spore-producing bacterium ; often occurring in chainlike formations ; found primarily in soil ; Bn. the blood group whose red cells carry the B antigen ; Bn. the 2nd letter of the Roman alphabet ; bn. (physics) a unit of nuclear cross section ; the effective circular area that one particle presents to another as a target for an encounter ; Bn. a logarithmic unit of sound intensity equal to 10 decibels ; Bn. a trivalent metalloid element ; occurs both in a hard black crystal and in the form of a yellow or brown powder ; Bn. originally thought to be a single vitamin but now separated into several B vitamins ; B batteryn. battery for supplying a constant positive voltage to the plate of a vacuum tube ; B celln. a lymphocyte derived from bone marrow that provides humoral immunity ; it recognizes free antigen molecules in solution and matures into plasma cells that secrete immunoglobulin (antibodies) that inactivate the antigens ; B complexn. originally thought to be a single vitamin but now separated into several B vitamins ; B horizonn. immediately below the A-horizon ; contains deposits of organic matter leached from surface soils ; B lymphocyten. a lymphocyte derived from bone marrow that provides humoral immunity ; it recognizes free antigen molecules in solution and matures into plasma cells that secrete immunoglobulin (antibodies) that inactivate the antigens ; B vitaminn. originally thought to be a single vitamin but now separated into several B vitamins ; B-52n. United States military aircraft ; B- stands for bomber ; B-complex vitaminn. originally thought to be a single vitamin but now separated into several B vitamins ;
