The word effect is often confused with affect.
To quote "Rob, Lyme Regis" from the BBC News Magazine:
- If you do something to change a situation, then you "effect" a change. If your circumstances are changed by an action, then the change has caused an "effect". You cannot "affect" a change in something, nor can you be "effected" by one.
The correct use of "effect" is usually as a noun, a synonym of result. In a less common use as a verb, it means to create the the result (not just to influence it as "affect").
- The effect of the rainstorm was an overflowing drain.
- The political rally was held to effect a change in the laws.
- His mood effected me.
- One of the affects of her better eating habits was weight loss.
- Grammar Girl's Quick and Dirty Tips on Affect Versus Effect