niacinamide \niacinamide\ 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]