Dotted circle

In Unicode, the dotted circle is a non-significant typographic character used to illustrate the effect of a combining mark, such as a diacritic mark. It can also be used to indicate a spot where a character is supposed to be, but it is rarely used for other purposes.

Illustration

A Unicode combining mark combines with a preceding character. When used as stand-alone, it would combine unintentionally with a preceding character :

Using the generic dotted circle character also shows the relative positioning of the diacritic.