Affect vs Effect: The Difference, and a Test That Works
2 min read
Short answer
The everyday rule
In nearly every sentence you will write, the choice comes down to the part of speech.
- Affect is a verb. It means to influence or change something. The delay affected everyone on the train.
- Effect is a noun. It means the result of a change. The delay had a knock-on effect for the rest of the day.
A common memory aid is A for action, E for end result: affect is the action, effect is what you end up with.
The article test
If the word follows a, an, the, any or an adjective, it is a noun, so it is effect.
| Sentence | Word before it | Answer |
|---|---|---|
| The new policy had an ___ on sales. | an | effect |
| Did the policy ___ sales? | (a verb slot) | affect |
| The side ___s were mild. | side (adjective) | effects |
| Cold weather can ___ your mood. | can (a verb slot) | affect |
If you can swap in influence and the sentence still works, you want affect. If result fits, you want effect.
The two exceptions
These are rarer, and they are why the rule is “usually” rather than “always”.
Effect as a verb means to bring about or to make happen, and it almost always appears with a word like change: The new manager effected real change. That means she caused the change. Compare The new manager affected the change, which means she influenced a change that was already happening. The two sentences say different things, so the spelling matters.
Affect as a noun is a term from psychology meaning a person’s visible emotional state: The patient presented with a flat affect. Unless you are writing clinical notes, you will rarely need it.
Common phrases
- Take effect — “The new rules take effect on Monday.” (noun)
- In effect — “The ban is still in effect.” (noun)
- Sound effects, special effects, side effects (nouns)
- Personal effects — belongings, as in “the hotel returned his personal effects.” (noun)
- Adversely affected — “Crops were adversely affected by the frost.” (verb)
Quick check
Try these before reading the answers.
- The medicine began to take ___ within an hour.
- How will the merger ___ your team?
- Lack of sleep has a real ___ on concentration.
Answers: effect, affect, effect.