The words "affect" and "effect" are often confused because they sound alike and have related meanings, although they're used differently. In most cases, "affect" is a verb and "effect" is a noun.
How to Use "Affect"
As a verb, "affect" has several meanings. The first and most common is, to influence, create a change, or alter something or someone. "Affect" also means to pretend to feel something (to "affect" sadness). In its original sense in Middle French, affecter meant to have a sad or unfortunate impression on, and when "affect" stands unmodified, it does typically mean to sadden.
In psychology and psychiatry, the term "affect" (with stress on the first syllable) is also a noun with the technical meaning "an expressed or observed emotional response." However, this term seldom appears in nontechnical writing.
How to Use "Effect"
"Effect," on the other hand, is usually a noun meaning the result or consequence of some action or event. The noun "effect" also means something that's intended to create a particular impression or feeling, as in "the 'effect' of flying." And it can mean to make operative, as in "the law will take 'effect' in January 2022," as well as to have an operative influence on, as it's used in "side effect" or "aftereffect." In addition, it may function as part of a well-established compound noun such as "Doppler effect" or "greenhouse effect."
The main confusion happens when "effect" is used as a verb, meaning "to cause." The difference is the strength of the verbs: "to affect change" means to have an impact on change, while "to effect change" means to create it.
The following are examples of when you might use the verb "affect" to mean influence:
- The heat affected my ability to think clearly.
- The sportsman was not affected by the crowd's booing in the stadium.
- Adverse publicity affected the outcome of the election.
- Volcanoes can temporarily affect the quality of the atmosphere.
"Affect" can also mean to put on or assume:
- Jane affected disdain for Pavel that she did not, in fact, feel.
- When you attend parties at the White House, you should affect an air of cool sophistication.
Use the noun "effect" to describe an outcome or result:
- The extreme heat had a devastating effect on my garden.
- The effects of the Black Death included the reduction of the population of Europe.
- One side effect of the medication is drowsiness.
Use the verb "effect" to mean to create, make happen or bring about:
- If you want to effect change in Washington, you have to vote.
- It is time to effect a revolution in table manners.
- It looks to me as if we have effected a tactical surprise.
How to Remember the Difference
The main difference between the most common uses of "affect" and "effect" is the part of speech. As Brian Klems points out in a "Writer's Digest" column, "affect" is an action, and both words begin with an "a"; an "effect" is the end result of an action, and both begin with an "e."
- "Affect; effect." The Chicago Manual of Style. 16th ed., University of Chicago Press, 2010, p. 264.
- Fogarty, Mignon. "Affect Versus Effect." Grammar Girl's 101 Misused Words You'll Never Confuse Again. New York: St. Martin's Griffin, 2011. p. 12.
- Klems, Brian A. "Affect vs. Effect." The Writer's Dig, 22 Jan. 2013.