Eidonomy is the scientific study of the visible exterior parts of living things. It contrasts, with anatomy, which deals with the unseen structures within a living body.

In modern science, eidonomy is a rather static field as anatomy usually provides more insight and discovery potential than eidonomy. However, it is still important to the study of inherited traits in genetics as eidonomic traits such as eye color, hair color and skin color are easy to trace in this matter and to apply to a given group of genes. It can also be important in determining speciation and defining new species.

Eidonomy at Wikipedia