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Rapidity

//ɹəˈpɪdɪti// noun

Noun

1
speed, swiftness; the condition of being rapid countable, uncountable
"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."
2
a rate that is rapid wordnet
3
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
4
A measure of the velocity of a particle in a beam relative to the beam's axis countable, uncountable

From rapid + -ity, from French rapidité, from Latin rapiditas.

Unscramble this word: rapidity