To accelerate means to speed up or go faster. When a car accelerates, the driver presses the gas pedal and the car moves more quickly. When a runner accelerates in the final stretch of a race, they push harder to increase their speed toward the finish line.

In science, acceleration describes any change in velocity. Scientists measure acceleration carefully: a rocket accelerates dramatically during launch, going from stillness to thousands of miles per hour in minutes. A baseball accelerates when the pitcher throws it, and then decelerates (slows down) as it travels through the air.

You can accelerate in ways beyond physical speed. A student might accelerate their learning by working extra hard, covering material faster than usual. A company might accelerate its timeline for finishing a project, finding ways to complete it sooner. When someone says “things are accelerating,” they mean events are happening faster or more intensely than before.

The opposite of accelerate is decelerate, meaning to slow down. Your bike decelerates when you squeeze the brakes. Scientists use these words precisely, but in everyday conversation, people often just say “speed up” and “slow down.” Still, accelerate adds a sense of power and intentionality: to accelerate is to actively increase momentum, whether you're racing down a track or working to master a difficult skill.