1. Any linear feature that appears on the surface of a rock. Lineation may be formed during deformation by the parallel alignment of minerals, fossils, or pebbles; by parallel crenulation cleavages; or by striations and grooves resulting from the movement of a rock over a plane, e.g. a fault surface (see slickenside), or flexural slip during folding. An intersection lineation is caused by the crossing of any two planes, e.g. cleavage and bedding.

2. Lineations are a series of parallel lines on a rock surface, formed by tectonic processes, by the transportation and deposition of sand under upper-flow-regime plane-bed conditions, or by the movement of glacial ice over the rock surface.