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Design
A generic circle shape.

Symbol

 * 1)  an unidentifiable/indeterminate segment
 * 2)  oxygen (Daltonian symbol)
 * 3)  a white stone
 * 1)  oxygen (Daltonian symbol)
 * 2)  a white stone
 * 1)  oxygen (Daltonian symbol)
 * 2)  a white stone
 * 1)  oxygen (Daltonian symbol)
 * 2)  a white stone

Etymology
Directly from 丸 'circle, circular'.

Noun

 * 1) circle
 * 2) correct, check mark, good

Antonyms

 * : incorrect, bad

Coordinate terms

 * : very good
 * : slightly wrong; OK but not great