The assumption of various distinct structural forms or shapes by a single organism or species.
Variations in size or in shape of a given (usually bacterial) species, due to conditions of environment, the pressure of antagonistic substances, or an inherent tendency in some species (e.g., streptobacillus).
The condition in which an individual assumes a number of different forms during its life cycle. The malarial parasite (Plasmodium) displays pleomorphism.