The ensō (円相 in Japanese) is a calligraphic painting of a circle in the Japanese ink-wash painting style, sumi-e. The line represents the universe and the area circumscribed represents the void (無). If the line is incomplete, it signifies continuing development; if the line is complete, it signifies perfection.

When the artist is ready, they empty their mind and become one with the emptiness of the paper canvas. Then they draw the ensō with a single brush stroke. The ensō so drawn encapsulates the spiritual state of the artist in the context of that moment.