Explain the following terms: - proportion - emphasis - form

All of these terms: proportion, emphasis and form are used in art to denote some design principles (proportion and emphasis) or elements of art (form).

Proportion refers to the relationship of  certain elements to the whole and to each other. Emphasis is the way of combining elements  and the part of the design that demands the most attention from the viewer. Form is an element of art that is three-dimensional and encloses  volume. It includes height, width and depth.