speed

(spēd)

noun

1. Physics The rate or a measure of the rate of motion, especially:
   a. Distance traveled divided by the time of travel.
   b. The limit of this quotient as the time of travel becomes vanishingly small; the first derivative of distance with respect to time.
   c. The magnitude of a velocity.
2. Swiftness of action.
3. a. The act of moving rapidly.
   b. The state of being in rapid motion; rapidity.
4. A transmission gear or set of gears in a motor vehicle.
5. a. A numerical expression of the sensitivity of a photographic film, plate, or paper to light.
   b. The capacity of a lens to accumulate light at an appropriate aperture.
   c. The length of time required or permitted for a camera shutter to open and admit light.
6. Slang A stimulant drug, especially amphetamine or methamphetamine.
7. Slang One that suits or appeals to a person's inclinations, skills, or character: Living in a large city is not my speed.
8. Archaic Prosperity; luck.

verb sped sped (spĕd) or speed·ed, speed·ing, speeds verb, transitive

1. To cause to go, move, or proceed quickly; hasten.
2. To increase the speed or rate of; accelerate: speed up a car; sped production.
3. To wish Godspeed to.
4. To further, promote, or expedite (a legal action, for example).
5. Archaic To help to succeed or prosper; aid.

verb, intransitive

1. a. To go, move, or proceed quickly: sped to the rescue.
   b. To drive at a speed exceeding a legal limit: was speeding on the freeway.
2. To pass quickly: The days sped by. The months have sped along.
3. To move, work, or happen at a faster rate; accelerate: His pulse speeded up.
4. Archaic
   a. To prove successful; prosper.
   b. To get along in a specified manner; fare.

Word History: We learn from the fable of the tortoise and the hare that the race is not always to the swift, but etymology teaches us that speed and success are closely related. The Old English word spēd, from which our word speed is descended, originally meant “prosperity, successful outcome, ability, or quickness.” A corresponding verb, spēdan, in Modern English the verb speed, meant “to succeed, prosper, or achieve a goal”; and an adjective, spēdig, the ancestor of our word speedy, meant “wealthy, powerful.” Except for archaic uses the words today relate only to the general sense of “velocity.” The meaning “success” is retained chiefly in the compound Godspeed, a noun formed from the phrase meaning “May God cause you to prosper.”