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The Collaborative International Dictionary
vitamin K3

vitamin K3 \vitamin K3\ n. menadione, ( C11H8O2) being chemically 2-methyl-1,4,-naphthoquinone. Having no side chain in the 3 position, it cannot exert all functions of a true K vitamin and the designation as vitamin K3 has been discouraged
--[MI11]

Syn: vitaminK2(0); menaphthone.

WordNet
vitamin K3

n. a form of vitamin K [syn: menadione]