Scale
Perceived size, understood only through comparison against another object or a known reference, not as an absolute measure.
In practice
Scale is how large something seems, which can only be judged against something else: a person, a hand, a familiar object or other elements nearby. A photo of a chair beside a person tells you its scale; the same chair alone on white could be a toy. Designers play with scale for effect, for example placing a tiny figure beneath a huge headline so the words feel monumental.
Often confused with Proportions
Scale is size relative to an outside reference; proportions are size relationships among the parts within one thing.
Try this
Photograph a small object close up with nothing for reference, then again with a coin beside it, and compare.