vitamin K

Main Entry: vitamin K
Function: noun
1 : either of two naturally occurring fat-soluble vitamins that are essential for the clotting of blood because of their rolein the production of prothrombin in the liver and that are used in preventing and treating hypoprothrombinemia and hemorrhage: a : a yellow oily naphthoquinoneC₃₁H₄₆O₂ that is obtained especially from alfalfa or made synthetically and that has a fast, potent, and prolonged biological effect, is effective orally, and is usefulespecially in treating hypoprothrombinemia induced by anticoagulant drugs called also phylloquinone, phytonadione, vitamin K₁; —see MEPHYTON b : a pale yellow crystalline naphthoquinone C₄₁H₅₆O₂ that is obtainedespecially from putrefied fish meal and is synthesized by various bacteria (as in the intestines of humans and higher animals) and that is much more unsaturated than vitamin K₁ and slightlyless active biologically called also menaquinone, vitamin K₂
2 : any of several synthetic compounds that are closely related chemically to vitaminsK₁ and K₂ but are simpler in structure and that have similar biological activity; especially : MENADIONE

vitamin K n.
Any of several fat-soluble compounds that are found in alfalfa, hog liver, fish meal, and vegetable oils and are essential for the production of normal amounts of prothrombin. Also called antihemorrhagic factor.