santimetre

Santimetre, more commonly spelled centimetre in English, is a unit of length in the metric system. It is defined as one hundredth of a metre, making 1 centimetre equal to 0.01 metres. The symbol for the unit is cm.

In the modern International System of Units (SI), the centimetre is a non-SI unit that is accepted for use with SI. It is derived from the metre, and because the metre is defined in terms of the speed of light, 1 centimetre remains exactly 0.01 metres by definition. The centimetre is widely used in everyday measurements and in many scientific fields for practical convenience, especially for objects whose dimensions fall between the scale of millimetres and metres.

Historically, the centimetre emerged with the development of the metric system in the late 18th and early 19th centuries as part of a decimal-based system designed to simplify measurement and calculation. It gained broad adoption across many countries and remains common in everyday contexts such as measuring human height, textiles, and small-scale engineering.

Usage and variation: the spelling differs by region. In British English and many other languages, the unit is written centimetre with the American English form centimeter. In some languages, the term is adapted with appropriate diacritics (for example, centimètre in French). The term remains a practical unit for expressing lengths in the range where metres are too large and millimetres too small.