If something affects a person or thing, it influences them or makes them change.

1. Fitness affects you mentally and physically, and how you feel affects everything from your relationships to your ability to cope.
2. One of the problems with noise is that it affects different people in different ways.
3. Emotional states can affect our hormone levels.

The noun from affect is effect. If something affects you, it has an effect on you.

4. …the effect of noise on people in factories.
5. …under the effect of the anaesthetic.

• If you effect something like a change or a repair, you cause the change to occur or the repair to be done. This is a fairly formal use, and is much less common than the use of effect as a noun.

6. She claimed that all her cures were effected solely by known medicines and by prayers.
7. Mrs Moffat had effected hasty repairs with tape and gummed paper.