noun

1. The state of moving quickly or the capacity for rapid motion; rapidity.

   “How does Usain Bolt run at that speed?”

2. The rate of motion or action, specifically / the magnitude of the velocity; the rate distance is traversed in a given time.

   “Speed limits provide information to the drivers about the safe speed to travel in average conditions.”

3. The sensitivity to light of film, plates or sensor.

Synonyms: DgammaDspot, gamma of the gamma, celerity, velocity