The Collaborative International Dictionary
vitamin K2 \vitamin K2\, vitamins K2 \vitamins K2\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..
Wiktionary
n. menaquinone
Wikipedia
Vitamin K or menaquinone has nine related compounds, generally subdivided into the short-chain menaquinones (with MK-4 as the most important member) and the long-chain menaquinones, of which MK-7, MK-8 and MK-9 are nutritionally the most recognized.