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Shade is the blocking of sunlight (in particular direct sunshine) by any object, and also the shadow created by that object. It may refer to blocking of sunlight by a roof, a tree, an umbrella, a window shade or blind, or anything else.
Shade is an important issue in temperate and tropical zones for providing cooling and shelter from the sun. Providing certain configurations of shading is an important passive solar technique. This may be done with overhangs, with shade trees, or with vines.
Shading using non-living materials blocks the sun, but also results in sunlight being absorbed and re-radiated as heat, or in sunlight being reflected as glare. Green plants, on the other hand, not only absorb a significant portion of the sunlight to invest as energy in photosynthesis to produce sugar, but also actively transpire, producing an additional cooling effect.
Shading is a process used in drawing for depicting different levels of blackness on paper by applying more pressure of the pencil for darker areas and less pressure for lighter areas. There are various techniques of shading including 'cross hatching' where perpendicular lines of varying closeness are drawn in a grid pattern in the area you wish to shade. The closer the lines are together, the darker the area will appear and vice versa.
Light patterns such as objects having a light side and having shade on the other side help creating on paper and on computer screens an illusion of relief/3D. Example:
Depending on the browser, the edges of the nine boxes typically are light on the upper and left side, and dark on the lower and right side of each. With a light background this means that mainly the lower side of horizontal edges and the right side of vertical edges are drawn. This suggests that the light comes from the upper left and that the nine boxes are at a lower level, with the edges protruding out of the screen.
See also 3D_computer_graphics#Reflection_and_shading_models.
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