Line will be used to capture the shapes, sizes, and their proportions.
Lines can be used as measuring scale. This measuring scale will decide the sizes of shapes and their proportions.
Without the help of measuring scale of line we won’t capture three dimensional illusion of space on our two dimensional picture space.
In nature we won’t see lines. We see only shapes. The trees, houses, clouds, animals and people …all are shapes. But they are having edges. Because of these edges their shapes, sizes and proportions will be decided. We call these edges as boundaries. These boundaries will be marked with lines.