Editing Radian (section)

=== Unit symbol ===
The [[International Bureau of Weights and Measures]]{{sfn|International Bureau of Weights and Measures|2019|p=151}} and [[International Organization for Standardization]]<ref>{{cite web |title=ISO 80000-3:2006 Quantities and Units - Space and Time |date=17 January 2017 |url=https://www.iso.org/standard/31888.html}}</ref> specify '''rad''' as the symbol for the radian. Alternative symbols that were in use in 1909 are <sup>c</sup> (the superscript letter c, for "circular measure"), the letter r, or a superscript {{sup|R}},<ref name="Hall_1909" /> but these variants are infrequently used, as they may be mistaken for a [[degree symbol]] (°) or a radius (r). Hence an angle of 1.2 radians would be written today as 1.2&nbsp;rad; archaic notations include 1.2&nbsp;r, 1.2{{sup|rad}}, 1.2{{sup|c}}, or 1.2{{sup|R}}.

In mathematical writing, the symbol "rad" is often omitted. When quantifying an angle in the absence of any symbol, radians are assumed, and when degrees are meant, the [[degree sign]] {{char|°}} is used.