The basic difference between them is that affect is chiefly used as a verb. Its main meaning is ‘to influence or make a difference to’, as in the following example sentences, all of which are taken from the Oxford English Corpus:
- Research suggests that the neighbourhood you live in can affect how well your children perform at school.
- The long periods of separation never affected her love for her mother.
- Continuous rain since mid-June has resulted in widespread flooding, affecting over 119 million people.
- He is in no doubt that thousands of people will be seriously affected if this proposal becomes a reality.
Effect is used as both a noun and a verb, though the noun use is much more common than the verb. As a noun, effect means ‘a result or an influence’:
- It was clear that the strong windy conditions were going to have an immediate effect on the result of the game.
- The beneficial effects of exercise are well documented.
- Corporations need to think about the long-term effects of their actions.
- The legislation had the effect of pushing up the cost of houses.
As a verb, effect means ‘to bring something about as a result’. It’s often used in quite formal contexts, such as written reports, rather than everyday English:
- The couple had been separated for two years, but her boyfriend tried to effect a reconciliation.
- A Royal Commission appointed in 1906 effected several reforms.
- Governments can mobilize the political will and resources to effect change when they choose to.
The key thing to remember is that affect is typically used as a verb:
- A bout of rheumatic fever in his youth had affected his health throughout his life.
On the other hand, effect is most commonly used as a noun:
- Participants were asked to volunteer for a study looking at the effects of stress on their health.
Need a reminder?
See our infographic for a quick visual illustration of the difference between affect and effect guide explaining the difference between affect and effect.