What is the difference between Niacin and Niacinamide?

Niacinamide (also called Nicotinamide), although it is considered another form of Vitamin B3, has a different chemical structure than nicotinic acid. It is a derivative of nicotinic acid, chemically named amide of nicotinic acid:

niacina

Niacin or nicotinic acid

niacinamide

Nicotinamide or Niacinamide