Rapidity

Definitions

1. speed, swiftness; the condition of being rapid
   countable, uncountable
2. A measure of velocity relative to the speed of light; defined as artanh(v), where artanh is the hyperbolic arctangent, and v = speed (with c = speed of light = 1).
   countable, uncountable
3. A measure of the velocity of a particle in a beam relative to the beam's axis
   countable, uncountable

Equivalents

Examples

“Although appreciating the rapidity and frequency of the Southern electric services I was now to use⟳ on short journeys, I became more than ever convinced that electric traction offers very little of interest⟳ to the dyed-in-the-wool railwayist.”

CEFR level