The sale is the relationship between the distances or lengths on the scale drawing or actual item. E.g a scale of 1 cm = 100 miles which means every cm on the map is equal to an actual distance of 100 miles. A scale factor may be used instead of a scale, one thing is that the scale factor has no units, instead a scale factor is a ratio example 1:40, which means the actual item is 10 times as large as the drawing.