Überstrich

Überstrich is the German term for an overline or macron: a horizontal line drawn above a letter or sequence. The designation is used across linguistics, typography, mathematics and computing to indicate context-specific meanings.

In linguistics and orthography, the Überstrich marks vowel length in phonetic transcription or in historical orthographies; long vowels may be shown as ā, ē, ī, ō, ū. It is common in language pedagogy and transliteration schemes to indicate phonemic length. In German, its use in modern standard orthography is limited to pedagogical or historical contexts.

In mathematics and logic, an overline denotes negation or complement: for example, Ā represents the complement of A in set theory; in some contexts it can mark closure. In decimal notation, a vinculum (bar) above digits indicates a repeating sequence, as in 0.̄3 or 0.\overline{3} for repeating decimals.

In typography and digital encoding, the Überstrich corresponds to the macron diacritic. Unicode provides the combining macron (U+0304) and precomposed characters such as ā (U+0101). The term is used in German-language typography and mathematical notation, distinct from other diacritics like the umlaut or the strikethrough.