Effect (noun) — a result, outcome, or change produced by an action or cause: "The new policy had a positive effect on attendance."
Effect (verb, formal) — to bring about or accomplish something, especially a change: "The committee effected several important reforms."
What Does Effect Mean?
Effect derives from the Latin effectus, meaning "accomplishment" or "result", from efficere — formed from ex- (out) and facere (to do or make). It entered Middle English in the 14th century via Old French effect, carrying its core sense of a result produced by an agent or cause. The same Latin root gives us efficient, effective, and the suffix -fy (as in clarify), all relating to making or producing something.
In modern British English, effect is overwhelmingly used as a noun. It names the outcome of an action: the effect of stress on health, a side effect of the medication, the greenhouse effect. The verb use — to effect change — survives in formal, legal, and academic writing but is rarely heard in everyday conversation.
The persistent confusion between effect (noun) and affect (verb) makes this one of the most-searched words in English grammar. Understanding the distinction clearly will sharpen your writing at every level from B1 upwards. See Cambridge Dictionary's full entry on “effect” for more examples.
Example Sentences
| Sentence | Level | Usage note |
|---|---|---|
| The medicine had no effect on his headache. | A2 | effect as result — simple noun use |
| The new policy had a positive effect on student attendance. | B1 | have an effect on — common collocation |
| Scientists are studying the long-term effects of air pollution. | B1 | plural effects; long-term effect collocation |
| The government's austerity measures had a knock-on effect throughout the public sector. | B2 | knock-on effect — chain reaction meaning |
| The new chief executive effected a radical transformation of the organisation's culture. | C1 | effect as formal verb — to bring about |
Collocations
| Collocation | Example |
|---|---|
| have an effect on | Stress can have a serious effect on your physical health. |
| take effect | The new regulations take effect from the first of March. |
| side effect | Drowsiness is a common side effect of this antihistamine. |
| in effect | The policy is, in effect, a complete reversal of previous guidance. |
| come into effect | The revised building codes come into effect next year. |
| knock-on effect | The train delays had a knock-on effect on the whole network. |
| greenhouse effect | Burning fossil fuels intensifies the greenhouse effect. |
| long-term effect | Researchers are investigating the long-term effects of the drug. |
| ripple effect | One factory closure can have a ripple effect across the local economy. |
| special effects | The film's special effects were praised by critics worldwide. |
Usage Notes
- Noun vs verb: In everyday English, effect is almost always a noun. The verb to effect (= to bring about) is confined to formal writing. If you mean "to influence", you want the verb affect, not effect.
- Effect vs affect: A quick test — can you replace the word with result? Use effect (noun). Can you replace it with influence? Use affect (verb). Example: The cold weather affected [influenced] the harvest. The frost had a devastating effect [result] on the crops.
- Article use: Effect usually takes the definite or indefinite article: an effect, the effect, the effects. The phrase to little effect (= without much result) is an exception where no article is used.
- Plural: Effects is commonly used when listing multiple outcomes: the effects of climate change, harmful side effects. It also appears in the fixed phrase personal effects (meaning belongings).
- Register: Effect as a verb is restricted to formal or academic contexts: legal documents, official reports, and business writing. Avoid it in informal communication where bring about or achieve sounds more natural.
Common Mistakes
Watch Out For
The new law will effect the way we travel. (wrong: effect used as verb meaning influence)
The new law will affect the way we travel. (affect = to influence — the common verb)
Smoking has a bad affect on your lungs.
Smoking has a bad effect on your lungs. (effect = result/outcome — the common noun)
The medicine took affect after an hour.
The medicine took effect after an hour. (take effect is a fixed phrase using the noun)
Related Words
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Frequently Asked Questions about “effect”
What does effect mean?
As a noun, effect means a result, outcome, or change produced by a cause: 'The medicine had an immediate effect.' As a verb (formal), to effect means to bring something about: 'The new manager effected a complete turnaround.' In everyday English it is used almost exclusively as a noun.
What is the difference between effect and affect?
Effect is usually a noun meaning result or outcome: 'The drug had no effect.' Affect is usually a verb meaning to influence or have an impact on: 'The noise affected my concentration.' A simple test: if you can replace the word with 'result', use effect; if you can replace it with 'influence', use affect.
Can effect be used as a verb?
Yes, but only in formal or academic contexts. To effect (verb) means to bring something into existence or cause it to happen: 'The new director effected sweeping reforms.' This use is uncommon in everyday speech. Do not confuse it with affect (the more common verb meaning to influence).
What are common collocations with effect?
Common collocations include: have an effect on, take effect, side effect, in effect, come into effect, knock-on effect, greenhouse effect, ripple effect, long-term effect, and special effects. These phrases appear frequently in academic, medical, and news writing.
Is effect countable or uncountable?
Effect is countable. You can say 'an effect', 'the effects', or 'several effects'. You would say 'The policy had several negative effects on the economy.' It is not normally used as an uncountable noun, though phrases like 'to little effect' (meaning without much result) treat it more abstractly.
What does 'in effect' mean?
'In effect' is a fixed phrase meaning 'in practice' or 'essentially': 'The new rule is, in effect, a ban on all outdoor events.' It signals that you are describing the practical reality of a situation, even if that is not the official or stated intention.
What does 'take effect' mean?
'Take effect' means to start working, to come into operation, or to begin to produce results: 'The anaesthetic took effect within minutes.' 'The new law takes effect on 1 January.' It is commonly used for medicines, laws, and policies.
What is the origin of the word effect?
Effect comes from Latin 'effectus', meaning 'accomplishment' or 'result', from the verb 'efficere' (to accomplish), formed from 'ex-' (out) and 'facere' (to do or make). It entered English in the 14th century via Old French 'effect'. The same Latin root gives us 'efficient', 'effective', and 'effectual'.
What is the adjective form of effect?
The main adjective forms are 'effective' (producing a desired result: 'an effective solution') and 'effectual' (more formal, achieving the intended purpose). The opposite is 'ineffective'. There is also 'ineffectual' (failing to produce results). The adverb is 'effectively'.
How can I practise using effect in English?
Try LexFizz's Complete the Sentence exercise to practise effect and affect in context, or use Flash Cards to memorise key collocations such as 'side effect', 'take effect', and 'have an effect on'. Reading news articles and academic texts is one of the best ways to see effect used naturally at B2–C1 level.