Overline

An overline or overbar or overscore (coined in analogy to underline and underscore, attested for mathematical notation since 1899), refers to the typographical feature of a line drawn immediately above the text, for example used to indicate medieval sigla. Specifically, a line drawn over one symbol is a macron, and a line over a collection of symbols is a vinculum. Marking one or more words with a continuous line above the characters is also described as "overstriking".

In Unicode the overline is represented by U+203E ‾ overline, and always functions as an independent symbol. The character U+0305 ◌̅ combining overline allows an overline to be placed over any character (as with any combining character, it appears over the preceding character: for example, x̅, compared to x‾). A series of overlined characters usually results in an unbroken line, depending on the font (for example, 1̅2̅3̅).

A similar character is U+00AF ¯ macron (also called "overbar"), and also has a combining variant, U+0304 ◌̄ combining macron, as well as a spacing modifier variant, U+02C9 ˉ modifier letter macron. The macron characters are shorter than their "overline" counterparts, and a series of macron characters usually do not result in an unbroken line (for example, 1̄2̄3̄). Unlike overline, the macron is present in the ISO/IEC 8859-1 and MS-DOS Codepage 850 encodings. Depending on the context in which it is used, the overbar has different meanings. The table to the right gives a summary of the different Unicode characters.

For East Asian (CJK) computing, U+FFE3 ￣ fullwidth macron is available. Despite the name, Unicode maps this character to both the U+203E ‾ overline and the U+00AF ¯ macron.

The Unicode character U+070F syriac abbreviation mark is used to mark in Syriac text a special overline with a dot at each end and the center, stretching from the position of the character to the end of the word. This line traditionally marks abbreviations and numbers. However, most computer systems do not render this line correctly or at all.