Mignon Fogarty (“Grammar Girl”) says her most requested grammar topic is the difference between “affect” and “effect.” Because we often get questions on that same topic, we’re devoting today’s blog post to helping you avoid mix-ups.
“Affect” is generally a verb or participle meaning “to influence.” “Effect” is generally used as a noun meaning “result.” The Mayfield Handbook of Technical & Scientific Writing and the University of Connecticut’s Style Points for Scientific Writing offer some useful examples:
- Temperature affects the growth rate of bacteria.
- Bacterial growth is affected by temperature.
- The effect of temperature on bacterial samples is being studied.
- Increased bacterial growth rate was one major effect of the rise in pond temperature.
- The release of hydrocarbons has had a significant effect on the depth of the ozone layer.
- The drug affected participants’ behavior.
- Our study showed that the drug had a large effect on behavior.
- The effects of the drug could be measured within five minutes of injection.
- Certain vitamins can have an instant effect on the immune system.
- It was found that certain vitamins affect the immune system.
Related to the noun “effect” are the adjective “effective,” the adverb “effectively,” and the noun “effectiveness.”
- The drug was effective a mere five minutes after injection.
- The medication effectively reduced tremors in the patient.
- The effectiveness of the medication could be assessed with blood testing.
Both “affect” and “effect” can have other uses.
“Affect” can be used as a noun, particularly in the field of psychology, to mean the facial expression or mood that someone appears to have.
- Researchers assessed the degree of positive and negative affect experienced by people as a result of their thoughts and day-to-day interactions.
- “Therapist’s Guide to Pediatric Affect and Behavior Regulation”
“Effect” can be used as a verb, meaning “bring about” or “accomplish.”
- The temperature reversal effected a major slowdown in the bacterial growth rate.
- Under the new administration, changes were effected in testing protocols.
Don’t allow mix-ups to affect the effectiveness of your writing!