speed

The word “speed” means how fast something moves, or the rate at which something happens. In plain terms, how quickly something moves or happens; also slang for amphetamine.

“Speed” is pronounced speed (/spiːd/ in IPA).

Here is “speed” used in a sentence: “The train reached a top speed of 200 miles per hour.”

Words with a similar meaning to “speed” include velocity.

Depending on how it is used, “speed” can be a noun and a verb.

The word “speed” comes from Old English. From Old English spēd ("success, prosperity"). Originally meant "good luck" or "success" — the "fast movement" sense developed later, still visible in the old phrase "Godspeed.".

“Speed” is a very common word in modern English, usually learned at around the A2 level.

“Speed” has 3 distinct senses listed in this dictionary. The most common is: how fast something moves, or the rate at which something happens.

In everyday use they mean the same thing, but in physics they differ. Speed measures only how fast something moves, with no direction. Velocity measures how fast and in which direction, making it a directional quantity. A car going 30 mph has a speed; the same car heading north at 30 mph has a velocity.

Speed is measured as distance travelled divided by the time taken, giving units like miles per hour, kilometres per hour, or metres per second. A speedometer shows a vehicle's speed directly. In science, average speed covers a whole journey, while instantaneous speed is how fast something is moving at a single moment.

There is no single perfect opposite, but slowness is the closest — a low rate of movement. Words like sluggishness and delay also contrast with speed when something moves or happens slowly. In physics, a lower speed simply means covering less distance in the same amount of time.