Definition:Linear Measure

Length
Length is distance measured in one direction. Usually, in multi-dimensional figures, the dimension in which the distance is longest is referred to as length.

Breadth
Otherwise called "width".

Breadth is distance measured in a second dimension, perpendicular to length and in the plane of the figure (in the case of a two-dimensional figure). In a three-dimensional figure, the choice of which direction is referred to as width is often arbitrary.

Depth
Depth is distance measured in a third dimension, perpendicular to both length and breadth. The choice of depth is often arbitrary, although in two-dimensional diagrams of three-dimensional figures, depth is usually the dimension perpendicular to the plane the figure is drawn in