vitamin A

noun

Definition of vitamin A

: any of several fat-soluble vitamins (such as retinol) that are found especially in green or orange vegetables (such as carrots or spinach) and in animal products (such as egg yolk, butter, or liver) and whose deficiency in the animal body causes epithelial tissues to become keratinous (as in the eye with resulting visual defects)

Recent Examples of vitamin a from the Web

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First Known Use of vitamin a

circa 1920


Medical Dictionary

vitamin A

noun

medical Definition of vitamin A

: any of several fat-soluble vitamins or a mixture of two or more of them whose lack in the animal body causes keratinization of epithelial tissues (as in the eye with resulting night blindness and xerophthalmia): as
a : a pale yellow crystalline highly unsaturated alicyclic alcohol C20H29OH that is found in animal products (as egg yolk, milk, and butter) and especially in marine fish-liver oils (as of cod, halibut, and shark) and that is used in various forms in medicine and nutrition called also retinol, vitamin A1
b : a yellow viscous liquid alicyclic alcohol C20H27OH that contains one more double bond in a molecule than vitamin A1 and is less active biologically in mammals and that occurs especially in the liver oil of freshwater fish called also vitamin A2

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