Affected describes something that has been influenced or changed, while effected is used when something is caused or brought about. These words are often confused because their meanings are closely related.
Affected is a past tense verb meaning to influence or produce an effect on something. It can also be an adjective describing something that has been impacted. For example, "The storm affected the power lines" shows how the storm influenced the power lines.
Effected is a past tense verb meaning to cause something to happen, usually through effort or action. For example, "The manager effected changes in the policy" means the manager caused changes to occur.
The key difference lies in whether something is being influenced (affected) or caused (effected). Affected is more commonly used in everyday language, while effected is more formal and specific.
Many people confuse affected and effected because they sound similar and both relate to causing change. However, affected is about being influenced, while effected is about causing that influence. For example, "The new law affected many people" is correct, but "The new law effected many people" is incorrect because the law influenced people, it didn't cause them to exist.
Consider these examples:
Another example: "The loud noise affected the baby's sleep," shows how the noise influenced the baby. "The nurse effected a quick recovery" shows how the nurse caused the recovery.
I once wrote, "The new policy will affect our daily routines," meaning the policy will influence our routines. A colleague corrected me, saying, "You mean it will effect our routines?" But that was incorrect because the policy influences, not causes, the routines.