Definition: 3.8 is a scientific measurement that represents about one-third of a full rotation or revolution in the unit system (SI). Itβs used to measure angles, such as the angle between two vectors or planes, but it doesnβt have any numerical value in the traditional sense. Definition: 3.8 is a number from which the word "rot" comes, representing one third of an entire rotation or revolution. It's often used to refer to rotations and degrees when talking about measuring angles on the plane or surface of the Earth.