It also involves the correct use of significant figures. They are units of structure or function which are useful in explaining certain phenomena. The cell is the basic unit of organic structure. The atom is the basic unit of molecular structure. This is a characteristic which stays constant even though other things may change.
Scale involves a change in dimensions.
This may affect other characteristics of a system. A paper airplane made from a sheet of notebook paper may fly differently than a plane of identical design made from a poster- sized sheet of the same paper. It is a mathematical framework in which it is convenient to describe objects and events. According to general relativity, gravity is not a force, but a property of space itself. It is a curvature in time-space caused by the presence of an object.