longueur

Longueur is a French noun that denotes the measurement extent in one dimension: the distance, size, or reach of an object or space. It can also refer to duration in time. The word comes from Old French longueur, ultimately from Latin longitudo, based on longus meaning long.

In everyday and technical usage, longueur covers a range of meanings. In geometry and everyday speech, the longueur of a segment is the distance between its endpoints, and the longueur of an object is its size along a given direction. People talk about the longueur d’une table, the longueur d’un voyage, or the longueur d’un vêtement to describe how long something is. In science, phrases such as longueur d’onde (wavelength) extend the concept to waves, describing the spatial period of a wave. In computing and information technology, one speaks of la longueur d’une chaîne (string length) or la longueur d’un fichier to indicate the amount of data or characters.

Commonly, lengths are measured in meters, but other units such as centimeters, kilometers, feet, or miles may be used depending on the country and field. The concept underpins metrology and standardization, with historical definitions of length evolving as measurement science advances. In French, longueur is contrasted with other dimensions such as largeur (width) and hauteur (height), and it remains a fundamental notion across science, engineering, and daily life.