A decameter is a unit of length measurement equal to ten meters, or approximately 32.8 feet. This unit of measurement is spelled differently in different places; it is often spelled decametre, dekametre, or dekameter in various European locales. The decameter is not a widely-used unit; lengths are usually measured in millimeters, centimeters, meters, and kilometers when the metric system of measurement is used, or in inches, feet, yards, and miles when imperial units are used. Decameters are commonly abbreviated to "dam" for simplicity; 15 meters, then, would be 1.5 dam, or 1.5 decameters. In scientific notation, one decameter is represented as 1.0 x 10^{1} meters or, more simply, ten meters.
"Deca" is one of the many prefixes used in the International system of units, usually abbreviated to the SI system, from the "Système International d'unités." As a prefix, it represents ten of whatever unit it is describing. Other possible prefixes include kilo, which represents 1,000, and centi, which represents one one-hundredth of a given base unit. In the case of the decameter, the meter is the base unit and "deca" states that measurements are being conducted in terms of ten meters. A kilometer, accordingly, represents 1,000 meters and a centimeter represents one one-hundredth of a meter.
Square decameters and cubic decameters are sometimes used to measure area or volume. One square decameter, or an area of ten meters by ten meters, is the same as 100 square meters. One cubic decameter, or ten meters by ten meters by ten meters, describes 1,000 cubic meters of three-dimensional space. Measurements of area and volume in decameters are abbreviated with dam^{2} and dam^{3}, respectively. To give some context, 1.62 square decameters roughly corresponds to the area of a volleyball field and one cubic decameter roughly corresponds to the volume of water contained within an Olympic-sized swimming pool.
While decameters are rarely used, there is one scientific niche that does occasionally utilize the generally-impractical unit. Decameters are commonly used in fields related to meteorology as a unit for the measurement of geopotential height a vertical coordinate relative to the earth's mean sea level that takes variables such as gravity and latitude into consideration. Geopotential height is important for some pressure-sensitive measurements and calculations that must be made with such measurements in the field of meteorology.