use-icon

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

use-icon

THE USAGE PANEL

The Usage Panel is a group of nearly 200 prominent scholars, creative writers, journalists, diplomats, and others in occupations requiring mastery of language. Annual surveys have gauged the acceptability of particular usages and grammatical constructions.

The Panelists

puzzle-icon

NEED HELP SOLVING A CROSSWORD PUZZLE?

Go to our Crossword Puzzle Solver and type in the letters that you know, and the Solver will produce a list of possible solutions.

open-icon

AMERICAN HERITAGE DICTIONARY APP

The new American Heritage Dictionary app is now available for iOS and Android.

scroll-icon

THE AMERICAN HERITAGE DICTIONARY BLOG

The articles in our blog examine new words, revised definitions, interesting images from the fifth edition, discussions of usage, and more.

100-words-icon

See word lists from the best-selling 100 Words Series!

Find out more!

open-icon

INTERESTED IN DICTIONARIES?

Check out the Dictionary Society of North America at http://www.dictionarysociety.com

ax·is (ăksĭs)
Share:
n. pl. ax·es (ăksēz)
1. A straight line about which a body or geometric object rotates or may be conceived to rotate.
2. Mathematics
a. An unlimited line, half-line, or line segment serving to orient a space or a geometric object, especially a line about which the object is symmetric.
b. A reference line from which distances or angles are measured in a coordinate system.
3. A center line to which parts of a structure or body may be referred.
4. An imaginary line to which elements of a work of art, such as a picture, are referred for measurement or symmetry.
5. Anatomy
a. The second cervical vertebra on which the head turns.
b. Any of various central structures, such as the spinal column, or standard abstract lines used as a positional referent.
6. Botany The main stem or central part about which organs or plant parts such as branches are arranged.
7. One of three mutually perpendicular lines that define the orientation of an aircraft, with one being along its direction of travel and the other two being perpendicular to the direction of travel.
8. A line through the optical center of a lens that is perpendicular to both its surfaces.
9. One of three or four imaginary lines used to define the faces of a crystal and the position of its atoms.
10.
a. An alliance of powers, such as nations, to promote mutual interests and policies.
b. Axis The alliance of Germany and Italy in 1936, later including Japan and other nations, that opposed the Allies in World War II.

[Middle English, from Latin.]

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 

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.

This website is best viewed in Chrome, Firefox, Microsoft Edge, or Safari. Some characters in pronunciations and etymologies cannot be displayed properly in Internet Explorer.