HOW TO USE THE DICTIONARY

To look up an entry in The American Heritage Dictionary of the English Language, use the search window above. For best results, after typing in the word, click on the “Search” button instead of using the “enter” key.

Some compound words (like bus rapid transit, dog whistle, or identity theft) don’t appear on the drop-down list when you type them in the search bar. For best results with compound words, place a quotation mark before the compound word in the search window.

guide to the dictionary

vitamin K

A fat-soluble vitamin, found in leafy green vegetables and some animal products and produced by intestinal bacteria, that plays an essential role in blood clotting. It exists in two main forms, K₁ and K₂.

[Abbreviation and partial translation of German K(oagulations)vitamin, coagulation vitamin, clotting vitamin, from Koagulation, coagulation, from Latin coāgulātiō, coāgulātiōn-, from coāgulāre, to curdle, coagulate; see COAGULATE.]

vitamin K₃

See menadione.

vitamin K₂

Any of several fat-soluble compounds found in liver and other animal products and in some fermented foods and synthesized in the body by intestinal bacteria. Also called menaquinone.

vitamin K₁

1. A yellow viscous oil, C₃₁H₄₆O₂, found in leafy green vegetables and used by the body in the synthesis of prothrombin. Also called phylloquinone.

2. A synthetic analog of this vitamin, used in the treatment of some coagulation disorders and to prevent hemorrhagic disease in newborns. In veterinary medicine, it is used as an antidote to poisoning by anticoagulant rodenticides. Also called phytonadione.

Indo-European & Semitic Roots Appendices

Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

Indo-European Roots

Semitic Roots

The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.

American Heritage Dictionary Products

HOW TO USE THE DICTIONARY

THE USAGE PANEL

AMERICAN HERITAGE DICTIONARY APP

THE AMERICAN HERITAGE DICTIONARY BLOG

INTERESTED IN DICTIONARIES?

Indo-European & Semitic Roots Appendices

American Heritage Dictionary Products