The rule
| Word | Usually | Means | Example |
|---|---|---|---|
| affect | verb (an action) | to influence or change something | Lack of sleep can affect your memory. |
| effect | noun (a thing) | a result | Lack of sleep has a big effect on memory. |
| Wrong | Right | Why |
|---|---|---|
| The new rule had a big affect on attendance. | The new rule had a big effect on attendance. | After a big, you need a noun: effect. |
| How did the move effect you? | How did the move affect you? | You need a verb meaning influence: affect. |
| The side affects include headaches. | The side effects include headaches. | Side effects are results, so the noun. |
The two rare uses
- Effect as a verb means to bring about or to cause to happen: The new principal wants to effect several changes. This is formal and fairly rare.
- Affect as a noun is used in psychology for the emotion a person shows: The patient had a flat affect. You will rarely need it in school writing.
Worked examples
Example 1: the a/an/the test
Problem The medicine had no (affect / effect) on my cough.
- Look before the blank: no. Can you put an there? The medicine had an ___ on my cough. Yes.
- A word that can follow an is a noun, so effect.
Answer The medicine had no effect on my cough.
Example 2: swap in influence
Problem Does music (affect / effect) how well you study?
- Swap in influence: Does music influence how well you study? It fits.
- Influence is a verb here, so affect.
Answer Does music affect how well you study?
Common mistakes and fixes
| Mistake | Fix |
|---|---|
| Writing had an affect | After a, an, the, any or no, use effect. |
| Writing effected when you mean influenced | The storm affected our plans. Use effected only for brought about. |
| Writing affect change | To mean bring about change, the phrase is effect change. |
| Plural mix-ups | Special effects, side effects and sound effects are all nouns. |
Practice
Five affect or effect questions
Lack of sleep can ___ your memory.
- affect
- effect
- affects
- effects
Show answer
Answer: affect
After can, you need a base verb meaning influence: affect. Effect would mean bring about your memory, which makes no sense, and the -s forms do not follow can.
The new rule had a big ___ on attendance.
- affect
- effect
- affected
- effected
Show answer
Answer: effect
After a big, you need a noun meaning result: effect. The other choices are verb forms, and the noun affect is a psychology term that does not fit.
How did moving to a new school ___ you?
- effect
- affect
- affects
- effects
Show answer
Answer: affect
After did, you need a base verb meaning influence: affect. Effect you would mean bring you about, and the -s forms do not follow did.
The medicine's side ___ include headaches.
- affects
- affect's
- effect's
- effects
Show answer
Answer: effects
Side effects are results, so you need the plural noun effects. Affects is a verb form, and the apostrophe forms show ownership, which does not fit.
Which word means bring about in this sentence? The new principal wants to ___ several changes, such as a later start time.
- affect
- affects
- effect
- effects
Show answer
Answer: effect
When the meaning is to bring about, the verb is effect. Affect several changes would mean influence changes that already exist. The -s forms do not follow to.
Frequently asked questions
Is it affected or effected?
Almost always affected, meaning influenced: The snow affected our trip. Use effected only when you mean brought about: The protests effected a change in the law. If you can swap in influenced, write affected.
Is it impact or effect?
Both can be nouns meaning a result: a big effect, a big impact. Impact also suggests force or a collision. In school writing, effect is often the plainer choice, and affect is the plainer verb than impact.
Why do so many people mix them up?
They sound almost the same, and both are about change and results. The verb and noun pattern solves most cases: an action is affect, a thing is effect. The rare uses are worth knowing but seldom needed in school writing.
Sources
- Purdue OWL, Spelling: Common Words that Sound Alike, accessed October 1, 2026
- Purdue OWL, Affect/Effect Exercise, accessed October 1, 2026
