 Combining character

A combining character is an encoded text character intended to combine with another character in its written presentation. A familiar case is U+0301 COMBINING ACUTE ACCENT: the sequence e followed by that code point represents an accented letter without requiring a separate precomposed code point for the whole letter.^[ref]

The same acute-accent code point can mark a distinct letter, stress or tone in different languages. Those functions do not require a different encoding of the accent in every language. Text shaping determines how the selected glyph is attached to the base shape, and glyph positioning can place additional marks relative to earlier marks.

A combining sequence and a grapheme cluster are related but distinct notions. The default segmentation rules determine which code points an editor treats as one unit. Unicode normalization addresses equivalence between encodings, such as a precomposed accented letter and a base-plus-accent sequence; it does not perform the geometric placement of their glyphs.