Any graphic character except for those with the General Category of Combining Mark (M). In a combining character sequence, the base character is the initial character, which the combining marks are applied to.

• Most Unicode characters are base characters. In terms of General Category values, a base character is any code point that has one of the following categories: Letter (L), Number (N), Punctuation (P), Symbol (S), or Space Separator (Zs).
• Base characters do not include control characters or format controls.
• Base characters are independent graphic characters, but this does not preclude the presentation of base characters from adopting different contextual forms or participating in ligatures.
• The interpretation of private-use characters (Co) as base characters or not is determined by the implementation. However, the default interpretation of private- use characters should be as base characters, in the absence of other information.