Nonspacing

Nonspacing, in typography and Unicode, refers to characters that do not occupy a distinct position on the line but modify the preceding character. These are typically combining marks, such as diacritics and tonal marks, which are applied to base letters after they are typed. They are encoded as nonspacing marks with the general category Mn (Nonspacing Mark) in Unicode.

Nonspacing marks do not advance the cursor; they attach to the base character and influence glyph composition rather than spacing. They can be stacked to produce multiple diacritics on a single letter, and they appear across many scripts, including Latin, Cyrillic, and other alphabets using combining marks. They are distinct from spacing marks (category Mc), which occupy space in the text layout.

Unicode provides both precomposed characters, which appear as single code points (for example Á), and decomposed sequences, where a base letter is followed by one or more nonspacing marks (A + U+0301). Canonical combining classes determine the preferred ordering of multiple marks to ensure stable rendering across fonts and platforms.

Processing text with nonspacing marks involves normalization, rendering, and search. Normalization converts between composed and decomposed forms; rendering requires fonts that provide appropriate diacritic glyphs and correct mark placement; search or collation may require treating marks as distinct or equivalent depending on the context.

Nonspacing marks enable accurate representation of many languages and phonetic notations, while keeping base characters compatible with older systems. They illustrate how diacritic information can modify a character without introducing additional spacing, supporting compact and expressive text encoding.