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

ar·a·chi·don·ic acid

(ăr′ə-kĭ-dŏnĭk)

An unsaturated fatty acid, C₂₀H₃₂O₂, present in animal fats and synthesized by the body from linoleic acid, that is essential in human nutrition and is a precursor in the biosynthesis of some prostaglandins.

[From arachidic, of the groundnut, from New Latin Arachis, groundnut genus, from Greek arakis, arakid-, diminutive of arakos, a leguminous plant.]

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