In Zen Buddhism, an ensō (円相 ) is a circle that is hand-drawn in one or two uninhibited brushstrokes to express a moment when the mind is free to let the body create.
The ensō symbolizes absolute enlightenment, strength, elegance, the universe, and mu (the void). It is characterised by a minimalism born of Japanese aesthetics.
Drawing ensō is a disciplined practice of Japanese ink painting—sumi-e (墨絵 "ink painting"). The tools and mechanics of drawing the ensō are the same as those used in traditional Japanese calligraphy: One uses a brush (筆 fudé) to apply ink to washi (a thin Japanese paper).