millimétert

Millimétert is the unit of length in the metric system equal to one thousandth of a meter. The standard symbol is mm. As a derived unit in the International System of Units (SI), the millimetre is widely used to express small distances in science, engineering, manufacturing, and everyday measurement.

Definition and relationships: 1 millimetre = 0.001 metres. The centimetre equals 10 millimetres, and the metre equals 1000 millimetres. The millimetre sits between the centimetre and the micrometre in the metric scale, and is commonly used for dimensions where centimetres are too large and metres too coarse. It forms part of the metric hierarchy that includes micrometres (µm) and kilometres (km).

Conversions and practical usage: 1 mm is approximately 0.03937 inches; 1 inch equals 25.4 millimetres. In practice, tolerances and measurements in manufacturing, engineering drawings, and product specifications are frequently given in millimetres or fractions of a millimetre, with tools like calipers and micrometre gauges used for precision.

History and standardization: The millimetre arose with the development of the metric system in the 18th and 19th centuries and is defined by the metre, which since 1983 is defined in terms of the speed of light. As a widely used derived SI unit, the millimetre remains a standard unit for describing small lengths worldwide, with common real-world references such as the thickness of credit cards and the approximate thickness range of human hair.