A line is a conceptual reference to a point in motion, a series of adjacent points, a connection between points, or an implied connection between points. A line has length but no width. Much like a point, the visual representation of a line does possess width, though typically very little width. A line can be straight, curved, move in one direction or change direction, be continuous or interrupted.

In terms of visual perception, a line can be seen as a crack in a sidewalk, telephone wires against the sky, or bare tree branches in winter. There are many essential lines in a design that are never marked and such lines are often referred to as implied lines.

Alternate terms: contour