I was grading papers recently and several students used the word affect when they meant effect, and vice versa. This is a very common error that I see often and I thought it’s time that I share my tricks for differentiating between the two words.
Effect and affect look and sound similar but they behave differently in a sentence and they pair up with different words. For example, we could write:
The aphrodisiac didn’t have an effect on him although alcohol will always affect his performance.
However, we can’t swap them around like this:
The aphrodisiac didn’t have an *affect on him although alcohol will always *effect his performance.
How do we differentiate these words from each other? For starters, effect is usually a noun.
He hoped that the aphrodisiac would have the desired effect.
This means that effect can be preceded by the or an (known as “articles”), such as the effect or an effect, and adjectives, such as a desired effect. Effect appears in many idioms too, like a snowball effect and cause and effect.
Effect is mostly a noun, while affect is mostly a verb.
When he has too much to drink it will affect his performance.
This means that affect has the basic, unmarked (infinitive) form to affect, and that it can be preceded by words such as will or can (auxiliary verbs). Affect can be modified to indicate tense, to create (inflected) words such as affects, affected, and affecting.
So, effect and affect mostly belong to different word classes; nouns and verbs respectively. I’ve used caveats like “usually” and “mostly” because we’re talking about language so there are exceptions to the rules, of course.
You’ve probably seen or heard effect used as a verb in phrases such as to effect change or to effect an arrest. The key to differentiating effect here is that it takes “to” (the particle), as in to effect the will of the people.
There is also a noun form of affect that is a technical term used in psychology, but in everyday use, affect used as a noun is mostly obsolete.
I’m always talking about how linguists describe language, but don’t prescribe language. That is, we talk about how people communicate but we don’t tell people how they should supposedly talk and write. This remains true, although linguists are interested in errors between effect and affect, or punctuation errors such as confusing there, their and they’re, because these errors can effect, I mean, these errors can affect meaning.