line
noun
a mark or stroke long in proportion to its breadth, made with a pen, pencil, tool, etc., on a surface: a line down the middle of the page.

• Contour lines
• Hatching and cross-hatching
• Gestural lines
• Implied lines
• Expressive lines

Line

Line is a mark made by a pointed tool - brush, pencil, stick, pen, etc. - and is often defined as a moving dot.

It has length and width, but its width is very thin compared to its length.

A line is created by the movement of a tool and pigment, and often suggests movement in a drawing or painting.

Line in Fine Art

Mark Tobey - "Geography of Phantasy", 1948

Tobey's painting is all line. He actually drew with his brush, then repeated lines creating a complex pattern. Tobey's lines are the subject of the painting and are not used to outline shapes or objects.

Source: Elements and Principles of Design: Student Guide with Activities, published by Crystal Productions