In the term Milliradian, the prefix “Milli-” means 1/1000th and the root “radian” is the metric unit of angular measurement. So, 1 Milliradian is 1/1000th of a radian. A radian is an angle based on a circle’s radius, or half of its diameter. When the length of a section of a circle equals the radius of that circle, the resulting angle is a radian.
