◎

◎ U+25CE, ◎ BULLSEYE ← ◍ [U+25CD] Geometric Shapes ● → [U+25CF]

Translingual

Symbol

◎

1. (chemistry, obsolete) calcium ("lime", Daltonian symbol)

   Technically, this should be red: ◎. May also be typeset ⊚ or ⦾, depending on which character matches the size of the other elements.

Japanese

Etymology

Literally 二重丸, 'two times circle'. A doubling ○ for emphasis.

Symbol

◎(にじゅうまる) 

1. very good (better than ○)
2. (maps) city hall or other municipal building

   This use may be formatted with a heavy outer ring: