The phrase tan line refers to an area or areas of pronounce comparative paleness in relation to other areas of the body due to prolonged exposure to ultraviolet radiation, such as from the sun. The tanned or sunburned area is such that it becomes visually clear where on the body the person was exposed to the sun versus the place(s) s/he covered up while being exposed to the sun. Tan-line areas can occur more generally in almost any context where the human body is exposed to comparatively more sunlight in certain areas than in other areas.