S: (n) microradian (a unit of angular distance equal to one thousandth of a milliradian)
S: (n) milliradian (a unit of angular distance equal to one thousandth of a radian)
S: (n) radian, rad (the unit of plane angle adopted under the Systeme International d'Unites; equal to the angle at the center of a circle subtended by an arc equal in length to the radius (approximately 57.295 degrees))