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



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



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



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


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

Find out more!



Check out the Dictionary Society of North America at

af·fect 1 (ə-fĕkt)
tr.v. af·fect·ed, af·fect·ing, af·fects
1. To have an influence on or effect a change in: Inflation affects the buying power of the dollar.
2. To act on the emotions of; touch or move. See Synonyms at move.
3. To attack or infect, as a disease: Rheumatic fever can affect the heart.
n. (ăfĕkt)
1. Feeling or emotion, especially as manifested by facial expression or body language: "The soldiers seen on television had been carefully chosen for blandness of affect" (Norman Mailer).
2. Obsolete A disposition, feeling, or tendency.

[Middle English affecten, from Latin afficere, affect-, to do to, act on : ad-, ad- + facere, to do; see dhē- in the Appendix of Indo-European roots.]

Usage Note: Affect and effect are often confused because they sound alike and have related meanings. First, bear in mind that there are two words spelled affect. One means "to put on a false show of," as in She affected a British accent. The other affect, the one that is confused with effect, is both a noun and a verb. As a noun it is uncommon and means roughly "emotion." It is pronounced with stress on the first syllable rather than the second. Note that affect does not have a noun sense meaning "an influence that brings about a change." As a verb, affect is most commonly used in the sense of "to cause a change in:" the ways in which smoking affects health. The verb effect means "to bring about or execute": medical treatment designed to effect a cure. Its corresponding noun means "a result." Thus if someone affects something, there is likely to be an effect of some kind, and from this may arise some of the confusion. People who stop smoking will see beneficial health effects, but not beneficial health affects. The verbs produce important differences in meaning. The sentence These measures have been designed to effect savings implies that the measures will cause new savings to come about. Using affect in the very similar sentence These measures will affect savings implies that the measures will cause a change in savings that have already been realized.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.
af·fect 2 (ə-fĕkt)
tr.v. af·fect·ed, af·fect·ing, af·fects
1. To put on a false show of; simulate: affected a British accent.
a. To have or show a liking for: affects dramatic clothes.
b. Archaic To fancy; love.
3. To tend to by nature; tend to assume: a substance that affects crystalline form.
4. To imitate; copy: "Spenser, in affecting the ancients, writ no language" (Ben Jonson).

[Middle English affecten, from Latin affectāre, to strive after, frequentative of afficere, affect-, to affect, influence; see AFFECT1.]

af·fecter n.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. 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.