A vergence is the simultaneous movement of both eyes in opposite directions to obtain or maintain single binocular vision.Cassin B; Solomon S. Dictionary of Eye Terminology. Gainsville, Florida: Triad Publishing Company, 1990.
In structural geology, the vergence of a deformed rock is the direction in which the next antiform can be found. Geometrically the vergence is the up-dip direction of the bedding perpendicular to the planes of the regional foliation in the rock.
The vergence (typical symbol: L) of a light bundle in optics is the reciprocal of the distance between the point of focus and a reference plane. It is measured in dioptres (1 D = 1 m-1). Vergence can also be understood as a measure of the curvature of the optical wavefront.