n. (1929) [ from G. Koagulationsvitamin. ] either of two fat-soluble vitamins (vitamin K1 or vitamin K2) that help clot blood by participating in the fromation of prothrombin. Syn. -- naphthoquinone. [ WordNet 1.5 +PJC ]

n. one of the two K vitamins, (C31H46O2). It is fat-soluble and occurs naturally as the trans isomer. Chemically it is 2-methyl-3-phytyl-1, 4, -naphthoquinone.
Syn. -- phylloquinone, phytonadione, antihemorrhagic vitamin.. [ WordNet 1.5 +PJC ]

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 1.5 ]

n. one of the two K vitamins, actually a mixture of homologous fat-soluble substituted naphthoquinones (called menaquinones), (C11H7O2[ C5H8 ]nH), where n may be 1 to 13 but is mostly 7 to 9. The term is also used for synthetic compounds resembling vitamin K2 and having the same physiological action. The individual components of vitamin K2 are also referred to by the number of isoprenyl units in the side chain (the number n in the formula), as for menadione, having no units at that position of the naphthaquinone ring, and also called vitamin K2(0) (and also called vitamin K3). [ MI11 ]
Syn. -- menaquinones, antihemorrhagic vitamin.. [ WordNet 1.5 +PJC ]