Ensō (円相) is a Japanese word meaning “circle” and a concept strongly associated with Zen. Ensō is one of the most common subjects of Japanese calligraphy even though it is a symbol and not a character. It symbolizes enlightenment, strength, elegance, the Universe, and the void; it can also symbolize the Japanese aesthetic itself. As an “expression of the moment” it is often considered a form of minimalist expressionist art.
In Zen Buddhist painting, ensō symbolizes a moment when the mind is free to simply let the body/spirit create.