Vitamin-a

noun
1.
a yellow, fat-soluble, solid terpene alcohol, C 20 H 30 O, obtained from carotene and occurring in green and yellow vegetables, egg yolk, etc.: essential to growth, the protection of epithelial tissue, and the prevention of night blindness.
noun
1.
a yellow oil, C 20 H 28 O, similar to vitamin A, obtained from fish liver.
noun
1.
a fat-soluble yellow unsaturated alcohol occurring in green and yellow vegetables (esp carrots), butter, egg yolk, and fish-liver oil (esp halibut oil). It is essential for the prevention of night blindness and the protection of epithelial tissue. Formula: C20H30O Also called vitamin A1, retinol
noun
1.
a vitamin that occurs in the tissues of freshwater fish and has a function similar to that of vitamin A. Formula: C20H28O Also called dehydroretinol

vitamin A n.
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 with deficiencies causing hardening and roughening of the skin, night blindness, and degeneration of mucous membranes. Also called retinol.

vitamin A2 n.
A golden yellow oil occurring chiefly in the livers of freshwater fish and having about 40 percent of the biological activity of vitamin A1.
vitamin A
A fat-soluble vitamin important for normal vision, tissue growth, and healthy skin. It is found in fish-liver oils, milk, green leafy vegetables, and red, orange, and yellow vegetables and fruits. A deficiency of vitamin A in humans causes poor vision at night and damage to the skin and mucous membranes. Also called retinol. Chemical formula: C20H30O.