Milliradian
Also: MRAD · Mil-Radian
An angular unit equal to one-thousandth of a radian, roughly 3.6 inches at 100 yards, used as the adjustment unit on milliradian turrets and reticles.
A milliradian is an angle equal to one one-thousandth of a radian, which works out to very close to 3.6 inches of spread at 100 yards, or 1 centimeter at 100 meters. As a scope adjustment unit it gives shooters a clean, decimal way to correct their aim: turrets graduated in milliradians typically move 0.1 mil per click, so ten clicks equal one full milliradian of subtension at any distance. This metric-friendly math is why the unit dominates modern long-range optics.
In everyday use the milliradian is simply called the mil, and the two words refer to the same angle, though purists reserve milliradian for the true mathematical unit. Compared to the minute of angle system, milliradian adjustments are coarser per click but pair naturally with mil-based reticles, letting a shooter measure a correction in the glass and dial the identical number on the turret without conversion.