Affect vs. Effect

These two words are very commonly confused, and while there are many accurate online explanations of the distinctions between them, most of those explanations only tell part of the story. The part that is most often told goes like this:

Affect is a verb meaning “to produce an effect on.” Effect is a noun meaning, generally, “result.” So, the price of cookies affects how many cookies I buy, and the effect of rising cookie prices is fewer cookies in my pantry.

So far so good, and that explanation goes deep enough for most common usage, but English is rarely so simple.

Affect as a verb can also mean “to make a display of liking or using” or “to put on a pretense of.” She affected indifference although her feelings were deeply hurt.

Affect (stress on the first syllable) can also be a noun meaning “the conscious subjective aspect of an emotion considered apart from bodily changes” or “a set of observable manifestations of a subjectively experienced emotion.” The patient displayed a completely emotionless affect.

Effect is also commonly used as a verb meaning “to cause to come into being” or “to bring about.” As governor, he effected statewide change.

There is still more to the story, if you include nuances like obsolete and other less common meanings, but I think this is enough confusion for one day.

(Definitions from The Merriam-Webster Dictionary.)