Effect is the result or consequence of something that happens. When you drop a ball, the effect is that it bounces. When you study hard for a test, the effect is usually a better grade. An effect is what comes after: the outcome, the change, or the impact.

The word shows up everywhere once you start noticing it. Scientists study cause and effect: what happens when you mix two chemicals, or how sunlight affects plant growth. Doctors prescribe medicine and monitor its effects on patients. When a school changes its lunch schedule, teachers watch for effects on student behavior and learning.

You might hear about special effects in movies (techniques that create illusions on screen), sound effects (artificial noises added to films or shows), or someone having an effect on you (meaning they influenced or changed you somehow). The greenhouse effect describes how certain gases trap heat in Earth's atmosphere.

People sometimes confuse effect with affect. Here's the key: affect (with an A) is usually the action of influencing something (“The weather affects my mood”), while effect (with an E) is the end result of that influence (“The effect of rainy weather is that I feel gloomy”). Think: Affect is the Action, Effect is the End result.

As a verb, effect means to bring something about or make it happen, especially a change (“The new principal effected several important reforms.”).