1. Occurrence of different forms of individual in a single species.

2. Occurrence of different structural forms in a single individual at different periods in the life cycle.

The property of a chemical substance crystallizing into two or more forms having different structures, such as diamond and graphite. Also known as pleomorphism.

The coexistence of genetically determined distinct forms in the same population, even the rarest of them being too common to be maintained solely by mutation; human blood groups are an example.