Measurement

Measurement is the process or the result of determining the ratio of a physical quantity, such as a length, time, temperature etc., to a unit of measurement, such as the metre, second or degree Celsius. The science of measurement is called metrology.

Definition

Measurement is the assignment of a number to a characteristic of an object or event, which can be compared with other objects or events. The scope and application of measurement are dependent on the context and discipline. In the natural sciences and engineering, measurements do not apply to nominal properties of objects or events, which is consistent with the guidelines of the International System of Units. This has the effect of making units of measurement matter, which can sometimes lead to confusion.

Units of measurement

A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other quantity of that kind can be expressed as a multiple of the unit of measurement. For example, a length is a physical quantity. The metre is a unit of length that represents a definite predetermined length. When we say 10 metres (or 10 m), we actually mean 10 times the definite predetermined length called "metre".

Systems of measurement

A system of measurement is a collection of units of measurement and rules relating them to each other. Systems of measurement have historically been important, regulated and defined for the purposes of science and commerce. Systems of measurement in modern use include the metric system, the imperial system, and United States customary units.

Measurement in science

In the natural sciences, measurement is essential to making quantitative observations. The increasing complexity of scientific research has led to significant developments in measurement methodologies, with efforts being placed on metrology and the creation of standards.

Measurement uncertainty

A measurement result is generally not complete unless it has an associated measurement uncertainty. The uncertainty establishes the limits within which the true value lies.

See also

• International System of Units
• Metrology
• Measurement uncertainty
• System of measurement
• Unit of measurement