What's the difference between 'affect' and 'effect'?

Question

Accepted Answer

**The simple rule:**

**Affect = verb** (to have an impact on something)
- "The rain affected the match." (the rain did something to the match)
- "Stress affects your sleep."

**Effect = noun** (the result or consequence)
- "The rain had a big effect on the match." (the result/consequence)
- "The side effects were minimal."

**Quick test:** Try replacing with "impact." If you'd use "impacted" → affect (verb). If you'd use "an impact" → effect (noun).

**The exceptions (native speakers get these wrong too):**
- "To effect change" — effect as a verb meaning "to bring about." Rare but correct.
- "The affects" — affect as a noun in psychology, meaning emotional response. Very specialised.

**Most common mistake:** "The decision effected everyone" — should be "affected."

**Register:** This distinction matters in formal writing. In casual speech, the wrong choice is rarely noticed.

**Tags:** grammar, affect vs effect, common mistakes, writing