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Word Usage: Affect and Effect

Just what is the difference between affect and effect? These two words are homonyms—words that sound alike but have different meanings. In this case, only one letter sets them apart.

To add to the confusion, both words can function as a noun or a verb. Knowing when to use each in a particular sentence can be a challenge.

Let's take a closer look at them in this word usage tip.


Affect is most commonly used as a verb and effect is most commonly used as a noun.

affect (verb): to act on or to influence

Drug A affected symptom severity.

effect (noun): an outcome, influence, or consequence

Drug B has no effect on glucose levels.

Sometimes, however, affect is used as a noun and effect as a verb. These uses are far less common than those described above.

affect (noun): a feeling or emotion (primarily in psychology)

The participant showed an unusual affect in response to the photo.

effect (verb): to bring about or to cause

The treatment effected a change in lung function.

Quick Tips: Affect vs Effect

Speedy pencil: quick grammar tips

Try the following memory aid for affect as a verb and effect as a noun:

  • A person or object acts on (affects) something.

  • A person or object causes an event (an effect).

  • Source

    Merriam-Webster's Collegiate Dictionary. 11th ed. Springfield, MA: Merriam-Webster, Inc.; 2007.

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    More Homonyms

    These homonyms are not pronounced exactly the same, but can be confused nonetheless. A dictionary (not your computer spell-checker) will help you make the correct word choice.









    For another example of homonyms, check this usage tip on its/it's.

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