vitamin A

A fat-soluble vitamin or a mixture of vitamins, especially vitamin A₁ or a mixture of vitamins A₁ and A₂, occurring principally in fish-liver oils, milk, and some yellow and dark green vegetables, and functioning in normal cell growth and development. Its deficiency causes hardening and roughening of the skin, night blindness, and degeneration of mucous membranes. Also called retinol.

A yellow crystalline compound, C₂₀H₃₀O, extracted from egg yolks, milk, and cod-liver oil.

A golden yellow oil, C₂₀H₂₈O, occurring chiefly in the livers of freshwater fish and having about 40 percent of the biological activity of vitamin A₁.