alaviivaa

Alaviiva, in Finnish alaviiva, is a symbol commonly referred to as the underscore in English. It is a short horizontal line that sits on the baseline of the text and is used in writing and computing for various purposes. The name and concept derive from its appearance and function as a line placed under other characters.

In terms of encoding, the underscore is represented by the Unicode code point U+005F and by the ASCII value 95. In Unicode it is officially named LOW LINE, and it is widely supported across fonts and systems. Visually it is distinct from a hyphen and is not used to indicate word breaks in typical typography, but rather as a character itself or as a connector in identifiers and file names.

Common uses include naming conventions in programming, where underscores separate words in identifiers (for example snake_case in Python). They are also used in file names, data schemas, and user handles. In URLs, underscores are allowed in path segments but are not permitted in domain labels, which affects their use in web addresses. Some languages and frameworks reserve certain underscore patterns for special purposes, such as private or built-in methods in Python, or implementation-specific identifiers in C and C++.

Historically, the term alaviiva reflects the idea of a line drawn underneath, aligning with the broader concept of emphasis in traditional typography. The underscore continues to be a practical tool in both technical and everyday contexts, balancing readability for humans with machine-readability in code and data.

See also: Unicode, ASCII, snake_case, domain naming conventions, programming naming conventions.