- Amorphous, nonproteinaceous pigment responsible for the brown hue of eyes, skin, hair, various tumors, and certain internal structures including the substantia nigra of the brain.
Definition from: CRISP Thesaurus via Unified Medical Language System at the National Library of Medicine
- Pigments causing darkness in skin, hair, feathers, etc. They are irregular polymeric structures and are divided into three groups: allomelanins in the plant kingdom and eumelanins and phaeomelanins in the animal kingdom.
Definition from: MeSH via Unified Medical Language System at the National Library of Medicine
- The substance that gives color to skin and eyes.
National Cancer Institute
Related discussion in the Handbook
See also Understanding Medical Terminology.