Confusion between the homophones affect and effect is common, but their distinctions are simple.
Affect
Affect is easy. It is almost always a verb, meaning to influence or to have an effect on—for example:
Here in Canada, metrophobia has not seemed to affect the sales of Christian Bök’s experimental poem Euonia . . . [Quill and Quire]
In a less common sense, affect can also mean to put on a false show of:
The book affects an air of empirical, science-based analysis, but unfortunately Johnson wants it on the cheap. [Guardian]
Affect also has a rarely used noun definition—namely, a feeling or emotion, especially as expressed through body language. We can’t find any examples of this sense of affect used correctly, but we’ll keep looking. Let us know if you find one.
Effect
Effect is a little more complicated. It’s usually a noun meaning something brought about by a cause, but it also has a verb meaning—to bring about.
Affect and the noun effect are confused often enough to keep editors busy, but the verb form of effect is almost never used correctly. The most common mistake comes with the phrase effect change (meaning to bring about change), which is often mistakenly written as affect change—for example:
His genuine desire to affect change was thwarted by a system which is stale and often ineffectual. [Independent]
Via the Wall Street Journal, here’s an example of correct usage of effect change:
But the 2,500 who attend Davos include very many individuals who have the power to effect change.
