A substance which is similar to another in crystalline form and composition.

Two compounds that have the same crystal structure, but diferent compositions. Examples: halite/sylvite, forsterite/fayalite, halite/galena.

same structure langue system belieing expression

An animal, plant, or group having superficial similarity to another, although phylogenetically different.

An isomorph is an organism that does not change in shape during growth. The implication is that its volume is proportional to its cubed length, and its surface area to its squared length. This holds for any shape it might have; the actual shape determines the proportionality constants.