n. A B vitamin (vitamin B5) essential for the normal function of the nervous system and the gastrointestinal tract. Called also nicotinic acid and antipellagra vitamin. Chemical formula C6H5NO2, chemically it is 3-pyridinecarboxylic acid. Syn. -- nicotinic acid. [ WordNet 1.5 ]
n. The amide of niacin (nicotinic acid), called also nicotinamide. It was at one time called vitamin B3, and can function to relieve nicotinic acid deficiency. Chemical formula C6H6N2O, chemically it is 3-pyridinecarboxamide. Syn. -- nicotinic acid amide, nicotinamide. [ PJC ]