Affect vs Effect
Affect is usually a verb meaning to influence or change something: 'Noise affects concentration.' Effect is usually a noun meaning a result: 'Noise has an effect on concentration.' The rare exceptions (effect as a verb meaning 'bring about' and affect as a psychology noun) are safe to ignore in everyday and IELTS English.
The rule
Affect vs effect at a glance
Affect
Effect
- Word class
- Verb, to affect
- Noun, an effect / the effect
- Meaning
- To influence, change, or have an impact on something
- A result, outcome, or consequence
- Typical pattern
- affect + object: rising prices affect households
- have an effect on + noun; the effect of X on Y
- Article test
- Never takes 'a/an/the' in front of it
- Usually follows 'a/an/the': a positive effect
- Quick swap test
- Swap in 'influence', if it still works, use affect
- Swap in 'result', if it still works, use effect
- Rare exception
- Affect as a noun in psychology: a flat affect
- Effect as a verb meaning 'bring about': effect change
Which one do I need?
Affect or effect?
Every answer at a glance
affect
Affect is the verb: it means to influence or change something. It takes an object and changes with tense: affects, affected.
Long commutes can affect how well students concentrate in class.
effect
Effect is the noun: a result. It usually follows a, an or the, as in 'have an effect on' or 'the effect of X on Y'.
The new cycle lanes have had a noticeable effect on air quality in the centre.
effect (formal verb)
In formal English, effect can be a verb meaning 'bring about'. It is rare and sounds official, so 'bring about' is often the safer choice.
Within a year, the new head teacher had effected real change in the school.
affect (psychology noun)
In psychology, affect is a noun for a person's visible emotional state. Outside that subject you will almost never need it.
The doctor noted that the patient's affect seemed flat during the assessment.
How to use affect vs effect
What's the difference between affect and effect?
Affect and effect sound almost identical, but in nearly every sentence you write or say, affect is the verb and effect is the noun. Affect means to influence, change, or have an impact on something: 'Poor sleep affects memory.' Effect means the result of that influence: 'Poor sleep has a negative effect on memory.'
A popular memory trick is RAVEN: Remember, Affect is a Verb, Effect is a Noun. If you can attach it directly to a subject and object like a normal verb, it's affect; if you can put 'a', 'an', or 'the' in front of it, it's effect.
- Long commutes affect people's stress levels.verb, affect + object
- Long commutes have a noticeable effect on stress levels.noun, effect follows 'a'
- Long commutes effect people's stress levels.→ affect (verb needed)
How do you test which word you need?
Two quick tests solve almost every case. First, try replacing the word with 'influence' or 'change': if the sentence still makes sense, you need affect. Second, check whether an article (a, an, the) or a possessive (its, their) sits directly in front of the word, that position always calls for the noun, effect.
These tests work because affect almost always behaves like an ordinary transitive verb, taking a direct object, while effect almost always behaves like an ordinary countable or uncountable noun.
- Caffeine can affect (= influence) how well you sleep.
- Caffeine can have a real effect on how well you sleep.'a' before the word signals the noun
- Doctors are studying the affects of caffeine on sleep.'the' before it needs the noun → the effects
Are there exceptions to the affect/effect rule?
Two rare exceptions exist, but you can safely avoid both in IELTS Speaking and Writing. Effect can be a formal verb meaning 'to bring about' or 'to cause to happen': 'The new manager effected several changes.' It always sounds official and is easily replaced by 'bring about' or 'make'.
Affect can also be a noun in psychology, meaning an observable emotional state: 'The patient showed a flat affect.' Unless you are writing about psychology specifically, you will never need this sense, for everyday and exam English, affect stays a verb and effect stays a noun.
- The reforms effected real change in the department.formal verb sense, rare, avoid unless confident
- The counsellor noted the client's affect during the session.psychology noun, a specialist use
Common mistakes with affect vs effect
Find what is wrong in each one, then open it to check.
1The new policy will effect thousands of workers.What's wrong? Show the fix
The new policy will affect thousands of workers.
The sentence needs a verb meaning 'influence', so it takes affect, not effect.
2The medicine had a strong affect on her energy levels.What's wrong? Show the fix
The medicine had a strong effect on her energy levels.
After 'a strong', the sentence needs a noun, effect, not the verb affect.
3Pollution effects marine life in serious ways.What's wrong? Show the fix
Pollution affects marine life in serious ways.
'Pollution' is the subject acting on 'marine life', so the verb affects is required.
4Researchers are still studying the affects of climate change.What's wrong? Show the fix
Researchers are still studying the effects of climate change.
'The' before the word signals a plural noun (effects) not the verb affects.
Practise
Write your own
Write a sentence that uses affect or effect, about you, your studies or your town.
Affect vs Effect in IELTS
Speaking
- Use affect as a verb when explaining causes in Part 3: 'Rising costs affect people's spending habits.' A Band 7 answer varies its verbs instead of repeating 'change' or 'influence' every time.
- 'Have a positive/negative effect on' is a flexible fixed phrase; dropping it into an answer signals natural range: 'Working night shifts has had a negative effect on my sleep.'
Writing
- Task 2 cause-and-effect essays depend on this pair constantly: 'Social media affects teenagers' mental health' versus 'Social media has a damaging effect on mental health.' Confusing the two is one of the most common Band 5 to 6 grammar slips examiners flag.
- Open a body paragraph with 'The effects of X on Y are...' as a strong topic sentence: 'The effects of urbanisation on air quality are well documented.'