Amines are categorized based on the number of carbon atoms directly bonded to the nitrogen atom. 

• Primary (1°) amineshave an alkyl or aryl group directly attached to the nitrogen. 
• Secondary (2°) amineshave two such groups. 
• Tertiary (3°) amineshave three. 

Amines can also be categorized as either aliphatic or aromatic based on the type of groups attached to the nitrogen atom. 

• Aliphatic amineshave only aliphatic (non-aromatic) groups attached. 
• Aromatic amineshave one or more aryl groups attached.