One is the action, the other is the result.
Verb. To have an influence on something or produce a change in it.
Stress affects your sleep quality.
El estrés afecta la calidad de tu sueño.
How does music affect your mood?
¿Cómo afecta la música tu estado de ánimo?
The cold weather affected the harvest.
El frío afectó la cosecha.
Noun. The result or consequence of an action.
The medicine had no effect on him.
La medicina no tuvo ningún efecto en él.
The effects of stress are well documented.
Los efectos del estrés están bien documentados.
Her speech had a powerful effect on the audience.
Su discurso tuvo un efecto poderoso en el público.
Common mistake
Using 'affect' as a noun or 'effect' as a verb. Wrong: "The medicine had a great affect on me."
Trick to remember it
Think of the initials: A for Affect = Action (verb). E for Effect = End result (noun).
Quick rule
If you can replace it with 'to influence', use affect. If you can replace it with 'result', use effect.
Did you know?
Though 'affect' is almost always a verb, in psychology it exists as a noun: 'flat affect' describes reduced emotional expression. This technical term is rarely used outside clinical contexts.
Exercise 1 · Pick the right one
The lack of sleep can ____ your concentration at work.
Exercise 2 · Pick the right one
The ____ of caffeine usually lasts about five hours.
Exercise 3 · Form the word
If you can replace it with 'to influence', use affect. If you can replace it with 'result', use effect.
Using 'affect' as a noun or 'effect' as a verb. Wrong: "The medicine had a great affect on me."
Think of the initials: A for Affect = Action (verb). E for Effect = End result (noun).
Bryan López
Founder of SpeakUP Academy