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Pronunciation: rat


  1. A record of the measurement of an event or process in terms of its relation to some fixed standard; measurement is expressed as the ratio of one quantity to another (velocity, distance per unit of time), or concentration formed per unit time.
  2. A measure of the frequency of an event in a defined population; the components of a rate are: the numerator (number of events); the denominator (population at risk of experiencing the event); and the specified time in which the events occur.

[L. ratum, a reckoning (see ratio)]

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© Copyright 2018 Wolters Kluwer. All Rights Reserved. Review date: Sep 19, 2016.