The linear relationship between the size of a model like a map and size of the real area it describes.  Scale is usually expressed as an RF (representative fraction) or by a scale bar which gives a graphical representation of the relationship, or both.  In general, large scale maps, such as 1:5,000 scale, show more detail and cover a smaller geographic area than small scale maps, such as 1:50,000, which cover large areas with less detail.