What is the difference between affect and effect?

The words affect and effect are commonly confused because they look and sound similar, but their roles in a sentence are different.

• Affect is usually a verb, meaning “to influence or make a difference to.” For example: “The rain will affect our travel plans.” Here, it describes the action of changing or influencing.
• Effect is usually a noun, meaning “the result or outcome of something.” For example: “The new policy had a positive effect on community safety.”

One memory trick: Affect = Action (verb), Effect = End result (noun).

However, in more advanced English, effect can also be used as a verb (meaning "to bring about" as in “to effect change”), and affect as a noun (in psychology, describing emotional expression). But in everyday English, sticking to the basic rule—affect = verb, effect = noun—will keep you accurate.

Examples:

• “The weather can affect my mood.”
• “Exercise has many positive effects on health.”