[koh-see-kuh nt, -kant]
noun Trigonometry.
  1. (in a right triangle) the ratio of the hypotenuse to the side opposite a given angle.
  2. the secant of the complement, or the reciprocal of the sine, of a given angle or arc. Abbreviation: csc
Also cosec.

Origin of cosecant

First recorded in 1700–10, cosecant is from the New Latin word cosecant- (stem of cosecāns). See co-, secant Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for cosecant


  1. (of an angle) a trigonometric function that in a right-angled triangle is the ratio of the length of the hypotenuse to that of the opposite side; the reciprocal of sineAbbreviation: cosec
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for cosecant

1706, from co, short for complement, + secant.

Online Etymology Dictionary, © 2010 Douglas Harper

cosecant in Science


  1. The ratio of the length of the hypotenuse in a right triangle to the length of the side opposite an acute angle. The cosecant is the inverse of the sine.
  2. The reciprocal of the ordinate of the endpoint of an arc of a unit circle centered at the origin of a Cartesian coordinate system, the arc being of length x and measured counterclockwise from the point (1, 0) if x is positive or clockwise if x is negative.
  3. A function of a number x, equal to the cosecant of an angle whose measure in radians is equal to x.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.