Melanin

n. dark pigment in the biochemical make-up of humans and animals which determines the darkness of skin and hair

Broadly, melanin is any of the polyacetylene, polyaniline, and polypyrrole "blacks" and "browns" or their mixed copolymers. The most common form of biological melanin is a polymer of either or both of two monomer molecules: indolequinone, and dihydroxyindole carboxylic acid. Melanin exists in the plant, animal and protista kingdoms, where it serves as a pigment. The presence of melanin in the archaea and bacteria kingdoms is an issue of ongoing debate amongst researchers in the field.
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Melanin /mel·a·nin/ any of several closely related dark pigments of the skin, hair, choroid coat of the eye, substantia nigra, and various tumors, [more]Melanin - Community and Resources

Noun
1. insoluble pigments that account for the color of e.g. skin and scales and feathers
(hypernym) animal pigment
(substance-holonym) skin, tegument, cutis
(derivation) melanize, melanise

n. melanin, dark pigment in the biochemical make-up of humans and animals which determines the darkness of skin and hair (Chemistry)