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Usage Glossary: A B C D E F G H I K L M N O P Q R S T U V W Y

affect/effect/impact

Do not confuse the words affect, effect, andimpact, each of which can be used both as a verb and as a noun. Avoidincorrectly using impact as a verb in place ofaffect or as a noun in place of effect.

Affect as a verb means "to influence."


The temperature affects the growth rate ofthe bacterial sample.

Affect as a noun has a specialized meaning in medicine andpsychology, referring to moods and feeling as distinct fromthoughts or knowledge.


Dua (1989) constructed the Thoughts and Real-LifeExperience Scale (THARL) to assess the degree of positive andnegative affect experienced by people as a resultof their thoughts and day-to-day interactions.

--J. K. Dua, "The Role of Negative Affect and Positive Affectin Stress, Depression, Self-Esteem, Assertiveness, Type ABehaviors, Psychological Health, and Physical Health," GenetPsychological Monographs


Effect as a verb means "to bring about, to produce," orto "accomplish something."


The temperature reversal effected a majorslowdown in the bacterial growth rate.

Effect as a noun means "result."


Increased bacterial growth rate was one majoreffect of the rise in pond temperature.

Impact as a verb means "strike with a blow" or "to packfirmly together."


The wisdom tooth impacted the molar.

Impact as a noun means "a collision."


The constant impact of the two gearmechanisms on each other eventually produced metal fatigue inseveral sprockets.


Do not use impact as a verb in place of "to affect."


Weak

The temperature impacts the growth rate ofthe bacterial sample.

Improved

The temperature affects the growth rate ofthe bacterial sample.


Do not use impact as a noun in place of "effect."


Weak

The release of hydrocarbons has had a significantimpact on the depth of the ozone layer.

Improved

The release of hydrocarbons has had a significanteffect on the depth of the ozone layer.


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