Input (grade 5): For example, an angle of 1.2 radians would be written as "1.2 rad" or "1.2 c" (the second symbol is often mistaken for a degree: "1.2 °").
Output (grade 6): It is shown by the symbol "rad" or, less often, c (for circular measure). A "milliradian" is 1/1000 of a radian.