Overstrekning

Overstrekning, in Norwegian, refers to the practice of placing a horizontal line above a letter, symbol, or group of characters. Also called an overline, it is a typographic and mathematical notation used to modify the meaning of the marked symbol. The specific interpretation of the line depends on the discipline and context.

In mathematics and logic, the overline is a common notation with several roles. It can indicate negation or the complement of a set (for example, Ā representing “not A” or the complement of A). It is also used to denote the closure of a set in topology (Ā), the complex conjugate of a number (z̄), and the mean or average in statistics (x̄). The overline therefore serves as a versatile shorthand across theories.

In other contexts, overstrekning is used in orthography and phonetics to mark features such as vowel length or tonal or phonetic distinctions in some languages, and in typography to convey emphasis in historical or specialized printing styles. The exact meaning is highly context-dependent.

Technical and typographic implementation varies. In digital text, an overline can be produced with a combining overline character (U+0305) or with the single-character OVERLINE (U+203E), depending on font support and rendering. Because meanings differ by field, readers rely on surrounding notation to interpret an overstrekning correctly.

See also: overline, macron, negation, set closure, complex conjugate, mean.