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O mark is the name of the circle symbol "◯".^{[citation needed]} It is often used in East Asia to express affirmation. Its use is similar to that of the checkmark ("✓") in the Western world. Its opposite is the X mark ("✗" or "×").

The symbol's names and meanings vary across cultures. In Japanese it is called marujirushi (丸印) or maru (丸) and expresses affirmation. In Korean it is called gongpyo (공표; 空標; lit. ball mark) and expresses affirmation.

Japan interprets the symbol as an affirmation.

Japan employs a number of related symbols (◎ ○ △ ×) in a system that expresses degrees of affirmation. A bullseye "◎" (nijūmaru; 二重丸) is often used for "excellent", the circle is a plain affirmation, the triangle "△" (sankaku; 三角) means "so-so" or "partially applicable", and the "×" expresses disagreement. This system is widely known in Japan, and thus often used without explanation. Ad-hoc adjustments are usually explained.

The hanamaru (花丸, 'flower O mark') is a variant of the O mark. It is typically drawn as a spiral surrounded by rounded flower petals, suggesting a flower. It is frequently used in praising or complimenting children, and the motif often appears in children's characters and logos. The hanamaru is frequently written on tests if a student has achieved full marks or an otherwise outstanding result. It is sometimes used in place of an O mark in grading written response problems if a student's answer is especially good. Some teachers add rotations to the spiral for exceptional answers.

This section contains Unicode emoticons or emojis. Without proper rendering support, you may see question marks, boxes, or other symbols instead of the intended characters.

Unicode provides various related symbols, including:

U+2B55 ⭕ HEAVY LARGE CIRCLE has both text and emoji presentations, as shown in the table. It defaults to emoji presentation.

The emoji U+1F4AE 💮 WHITE FLOWER looks similar to hanamaru, although it represents a rubber stamp commonly used to grade students' written answers and is not usually recognized as hanamaru.

• ○× quiz [ja] – true/false quizzes in Japan that use the O mark and its opposite
• Check mark
• Circle
• Geometric Shapes (Unicode block) – Block of Unicode symbols
• PlayStation controller – Game controller for the PlayStation
• Tic-tac-toe