vitamin A

n. retinol, yellow fat-soluble terpene alcohol found in liver oil and carotenoids (essential for growth and good vision)

Vitamin A is an essential human nutrient. It exists not as a single compound, but in several forms. In foods of animal origin, the major form of vitamin A is an alcohol (retinol), but can also exist as an aldehyde (retinal), or as an acid (retinoic acid). Precursors to the vitamin (a provitamin) are present in foods of plant origin as some of the members of the carotenoid family of compounds.
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Vitamin A n. A fat-soluble vitamin or a mixture of vitamins, especially vitamin A 1 or a mixture of vitamins A 1 and A 2, occurring principally in [more]Vitamin A - Community and Resources

Noun
1. any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes
(synonym) antiophthalmic factor, axerophthol, A
(hypernym) fat-soluble vitamin
(hyponym) vitamin A1, retinol

vitamin A, antixerophthalmic vitamin, vitamin found in animals, (synthesized in the liver from carotenoids)