/ ˈreɪdiən; NAmE / noun
( geometry ) a unit used to measure an angle, equal to the angle at the centre of a circle whose arc is the same length as the circle's radius
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WORD ORIGIN
late 19th cent.: from radius + -an .
/ ˈreɪdiən; NAmE / noun
( geometry ) a unit used to measure an angle, equal to the angle at the centre of a circle whose arc is the same length as the circle's radius
••
WORD ORIGIN
late 19th cent.: from radius + -an .
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005