- the occurrence of three forms distinct in structure, coloration, etc., among animals of the same species.
- the occurrence of three different forms of flowers, leaves, etc., on the same plant or on distinct plants of the same species.
- the property of some substances of crystallizing in three structurally distinct forms.
- the property or condition of occurring in three distinct forms.
- the property exhibited by certain species of having or occurring in three different forms
- the property of certain minerals of existing in three crystalline forms
