What is the Difference Between Affect and Effect?

girl sitting pensively holding her legs in bedroom.
In psychology, someone can be said to have "a neutral affect.". Arief Juwono / Getty Images

Affect and effect are difficult to keep straight. It may help to understand something about the derivation or etymology of the two closely related words..

Etymology (Derivation)

Affect and effect are both based on a very productive Latin word, facio, which means 'do, make' or any number of other things.

Affect is based on the Latin verb facio with the prefix ad- added.
Ad is a preposition meaning 'to, towards, near' and maintains some sense of that meaning when it is used as a prefix added to a verb.

Effect is based on the same Latin verb facio with the prefix ex- added.
Ex is a preposition meaning 'from, out of' and, again, maintains some sense of that meaning when used as a prefix added to a verb.

Affect doesn't look much like ad- + facio and effect looks little like ex- + facio. That's because

  1. the form of the verb facio that is used in the English is taken from the Latin verb's past participle, -fect. [TIP: Remember that in English the verb 'to do' has a past participle of 'done' and a past form of 'did'. 'Do, did', and 'done' don't all look alike. The same is true in Latin.]
  2. the consonant at the end of the prefix is assimilated to the following consonant.

Assimilation

To say that the end of the prefix is assimilated to the next consonant means:

  • the /d/ in ad- changes to /f/ and
  • the /x/ in ex- also changes to /f/.

Meaning

Affect (To, Towards)

  • Affect is based on a Latin word that means 'act on, have influence on, to do something to'. (The prefix ad results in acting on something.) Affect is both a noun and a verb.
  • The (transitive) verb is the more common form. Usually, the verb affect, with stress on the second syllable, means 'to act on, to produce an effect or change in'.

    Synonym of Affect as a Verb: 'To influence'.

  • The verb affect can also mean 'to make a pretense of'. Someone with a fake upper class accent has affected it and would be said to have an affectation.
  • The noun affect, with stress on the first syllable, means 'a mental state'.

    Synonym of Affect as a Noun: 'Feeling'.

Examples of Affect

  • Verb: Alcohol affects the liver.
  • Noun: He had a neutral affect. (Psychological jargon.)

Effect (Out of, From)

  • Effect is an English noun and verb based on a Latin word that means 'work out, accomplish'. (The prefix ex results in effects coming out of something else.)
  • The (transitive) verb effect means 'make happen, bring about, accomplish'.

    Synonym of Effect as a Verb: 'To produce'.

  • The English noun effect normally means 'results,' although sometimes it means 'household goods'. NOTE: You may affect an effect since affect is usually a verb. Effect as a verb is more common than affect as a noun.

    Synonym of Effect as a Noun: 'Outcome'.

Examples of Effect

  • Verb: He effected a change.
  • Noun: The effects of inflation include a reduction in discretionary spending.

Part III. Deciding Between the Two

Which Is It - Affect or Effect?

Follow these steps:

  1. Is it a (transitive) verb or a noun?
  2. If a noun,
    1. Is it psychological jargon?
    2. If psychological jargon, it may be affect, with an A
    3. If not psychological jargon, it's effect, with an E.
  3. If a verb, is 'accomplish' closer in meaning or is 'influence'?
    1. If a verb meaning accomplish, it's effect, with an E, unless it's an affectation.
    2. If a verb meaning influence, it's affect, with an A.