What does decametre mean?
The decametre is a metric unit of length equal to ten metres, abbreviated "dam" in the International System of Units. It sits between the metre and the hectometre on the metric scale, so that one hectometre contains ten decametres and one decametre contains ten metres. Despite being an officially recognised SI unit, it is seldom used in daily life, since lengths of around ten metres are almost always given simply in metres. Where it does appear, it tends to be in technical fields such as surveying, hydrology, and land measurement — notably because one square decametre equals an are, a traditional unit of area. British English typically spells the word "decametre", while American usage favours "dekameter". Learners often confuse it with the decimetre, which is one tenth of a metre rather than ten metres, making the two differ by a factor of one hundred.
nounA metric unit of length equal to ten metres, one tenth of a hectometre and one hundredth of a kilometre.
- A metric unit of length equal to ten metres (SI symbol: dam).
"The surveyor measured the field in decametres before converting to hectares."
"The swimming area was roped off at a depth of two decametres."
"One square decametre equals an are, a unit once widely used for measuring land."
In American English, the plural is typically spelled "dekameters" or "decameters".
"The bridge spanned three decametres across the narrow gorge."
Its official SI symbol is "dam" — making it possibly the only unit of measurement whose abbreviation is a real word.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of decametre
The word decametre derives from French décamètre, formed from the Greek prefix deka- meaning "ten" combined with mètre, itself from Greek metron meaning "measure". It entered English in the late eighteenth century alongside the other units created for the French Revolutionary metric system established in the 1790s. The same Greek root deka- appears in related English words such as decade, decimal, and decathlon.
How decametre is actually used
Spelled "decametre" in British English and usually "dekameter" or "decameter" in American English. It is rarely used in everyday contexts; most measurements of this scale are expressed in metres. The unit survives mainly in technical, surveying, and educational settings, and its multiples relate neatly to land measurement: one square decametre is one are.
Easily confused with decametre
A decimetre is one tenth of a metre (0.1 m), whereas a decametre is ten metres — a hundred times longer.