Affect is almost always a verb, meaning (1) to influence or to have an effect on, and (2) to put on a false show of. The first sense is far more common. Affect also has a rarely used noun definition—namely, a feeling or emotion, especially as expressed through body language.
Effect is usually a noun. It’s main definition is something brought about by a cause, but it also has a rarely used verb definition—namely, 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]
And this is correct:
But the 2,500 who attend Davos include very many individuals who have the power to effect change. [Wall Street Journal]
These writers use affect well:
Here in Canada, metrophobia has not seemed to affect the sales of Christian Bök’s experimental poem Euonia … [Quill and Quire]
The book affects an air of empirical, science-based analysis, but unfortunately Johnson wants it on the cheap. [Guardian]
And these writers use effect well:
Olympia Snowe is just the latest example in politics and business to demonstrate the ugly effects of incivility and why civility matters. [Boston Globe]
The effect seems to come from the keyboard itself – and is dubbed ‘the QWERTY effect’. [Daily Mail]
