Affect and effect are consistently among the most frequently looked up terms at Dictionary.com. The ongoing interest isn’t surprising: both of these words can be used as verbs and nouns, and their meanings overlap thematically. This slippery duo can send even experienced writers into a spiral of uncertainty—especially since many people pronounce them in almost the exact same way.
Let’s get to a basic guideline first: generally, we use affect as a verb (an action word), and effect as a noun (an object word).
The verb affect means “to act on; produce an effect or change in” as in, “the cold weather affected the crops.” It can also mean “to impress the mind or move the feelings of,” as in “the music affected him deeply.” So when you’re looking to use one of these two terms to express an action, chances are you’re looking for affect.
Effect is most commonly used as a noun, meaning “result” or “consequence.” So when you’re writing, try to swap out effect for result and see if it makes sense. For example, “exposure to the sun had the effect of toughening his skin.”
Effect might also catch you off guard because it appears in two common idioms: in effect, and take effect. It can also be used as a verb to mean “make happen,” but that use is less common.
Want to go deep? Much of the confusion surrounding this pair is due to a shared linguistic ancestor: both words have roots in the Latin verb facere meaning “to do, make.” Affect derives from the Latin verb afficere meaning “to do something to, to have influence on.” Effect descends from the Latin verb efficere, “to make, carry out.”
Sticking to the basic guideline of effect as a noun and affect as a verb will generally keep you in the good graces of your readers. But when you don’t know—we’re here for you.
Think you have the difference down? Take the quiz on affect vs. effect here.