Amine

Primary amine  Secondary amine  Tertiary amine     
An amine is a molecule which has a nitrogen atom that can behave as a base. An amine can be thought of coming from ammonia. The difference is that the three hydrogens in ammonia are changed to any group or atom. If only one of the hydrogens is changed, the amine is called primary. If two are changed, the amine is called secondary. If all three are changed then it is called tertiary. 

Sometimes, a fourth group can be added to the nitrogen. This is called a quaternary ammonium cation. This is not an amine but is a salt. If one of the groups on the nitrogen is a carbonyl group, then the molecule is called an amide. This has very different properties.

Amines are used a lot in chemistry. Since the nitrogen has a lone pair, it can do many reactions. It can take protons away from some acids. It can also be a nucleophile. It can be changed into imines and other functional groups.

Amines are also found in many proteins. They are a part of every amino acid.
References

Category:Functional groups
Category:Amines