Affect is usually a verb
Affect means to influence or make a difference to something. Example: “The weather can affect travel plans.”
Effect is usually a noun
Effect means a result or consequence. Example: “The new schedule had a positive effect.”
A quick substitution test
If you mean influence, try affect. If you mean result, try effect. Some specialist uses differ, but this test works for many everyday sentences.
Frequently asked questions
Can effect be a verb?
Yes. To effect something can mean to bring it about, as in “effect a change.” This is less common than the noun use.
Can affect be a noun?
Yes. In psychology, affect can refer to an observable emotional response or expression.