decametres

A decametre, symbol dam, is a unit of length in the metric system equal to ten metres. It is formed by the SI prefix deca- meaning ten, combined with the base unit metre. As a multiples unit, one decametre is 10 m, and 100 decametres equal 1 kilometre.

Usage: The decametre is among the metric prefixes attached to the metre, but it is not commonly used in everyday measurement. For most purposes distances are expressed in metres or kilometres; smaller lengths are expressed in centimetres or millimetres. In surveying, construction, or teaching about metric prefixes, decametres may appear as an example of a tenfold subdivision of the metre.

Spelling and symbols: The preferred term is decametre (British English) or dekameter (American English); the standard symbol for the unit is dam. The prefix deca- is abbreviated da, but when combined with metre the unit symbol is dam. The decametre is an SI-derived unit accepted for use with SI, although it remains uncommon in routine measurements. One kilometre equals 100 decametres.