Affect and Effect
Affect and Effect: A Troublesome Pair
Although affect and effect are spelled and sound similarly, their uses are very different.
Affect is a verb that means "to influence," and effect is a noun that means "an outcome" or "a result."
Use in Sentences
The medication adversely affected Mark's liver functioning.
Affected shows the action (verb) that the medication had on Mark's liver.
The medication had a detrimental effect on Mark's liver.
Effect refers to the outcome (noun) of the medication on Mark's liver.
This explanation seems pretty straightforward but there are exceptions. For example, in psychology affect is a noun that indicates mood or emotion such as "his affect was dark." And effect is sometimes a verb that means "to produce," "to create," or "to cause" as in the following example: "The medication should effect a positive change in his mood."
The Chicago Manual of Style, 15th Edition, The University of Chicago Press (2003)
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