Size Definition
Size constitutes the physical dimensions or magnitude of an object, and is a directly measurable attribute of visual quality.
(While size can be measured numerically, the apparent size of an object can change given context.)
Scale
A visual element’s inherent size measurement (expressed as meters, units, etc.)
Proportion
The size relationships between various elements of the design, or a percentage of a composition that an element takes up.
Ratio
the relative size between two elements, usually expressed as a fractional relation, such as 4:3 or 16:9.