rapidity

plural rapidities

1. countableuncountablespeed, swiftness; the condition of being rapid

   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.

   1944 November and December, Talisman, “A Broadening Horizon”, in Railway Magazine, page 340

   1 more example

   In clinical practice, the generation of diagnostic hypotheses occurs especially readily and rapidly in subdisciplines such as dermatology, where gross appearance of lesions is of particular importance diagnostically[…]. The primacy of macroscopy in paleopathology means that the activation of skeletal disease scripts occurs with similar facility and rapidity when skeletal remains are examined.

   2023, Simon Mays, “The Macroscopic Study of Human Skeletal Paleopathology” (chapter 2), in The Routledge Handbook of Paleopathology, Routledge, →DOI, →ISBN, pages 25–26

2. countableuncountablerelativityA 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).
3. countableuncountablenatural sciencesA measure of the velocity of a particle in a beam relative to the beam's axis