radian

UK:*UK and possibly other pronunciationsUK and possibly other pronunciations/ˈreɪdɪən/US:USA pronunciation: respellingUSA pronunciation: respelling(rā′dē ən)


WordReference Random House Unabridged Dictionary of American English © 2025
ra•di•an  (rā′dē ən),USA pronunciation n. [Math.]
  1. Mathematicsthe measure of a central angle subtending an arc equal in length to the radius: equal to 57.2958°. Abbr.: rad
  • radi(us) + -an 1875–80

Collins Concise English Dictionary © HarperCollins Publishers::
radian / ˈreɪdɪən/
  1. an SI unit of plane angle; the angle between two radii of a circle that cut off on the circumference an arc equal in length to the radius. 1 radian is equivalent to 57.296 degrees and π/2 radians equals a right angle
    Symbol: rad
Etymology: 19th Century: from radius
'radian' also found in these entries (note: many are not synonyms or translations):
SI unit - degree - milliradian - principal argument - rad - steradian

Forum discussions with the word(s) "radian" in the title:


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