chemical decomposition is the gradual fragmentation of a chemical compound into smaller molecules.

An example of decomposition would be: AB -> A + B

The stability that a chemical compound ordinarily has is eventually limited when exposed to extreme environmental conditions like for instance heat, radiation, humidity or the acidity of a medium. The decomposition process is generally not well defined and a molecule breaks up in a host of smaller fragments. Decomposition generally depends on the presence of amounts of oxygen or water.

Chemical decomposition is exploited in several analytical techniques notably mass spectrometry and thermal gravimetric analysis (TGA)