**Measurement** is the determination of the size or magnitude of something. Measurement is not limited to physical quantities, but can extend to quantifying almost any imaginable thing such as degree of uncertainty, consumer confidence, or the rate of increase in the fall in the price of beanie babies.

- "A measurement is a comparison to a standard." -- William Shockley

**measurement**is the process of comparing physical quantities of real-world objects and events. Established standard objects and events are used as units, and the measurement results in at least two numbers for the relationship between the item under study and the referenced unit of measurement, where at least one number estimates the statistical uncertainty in the measurement. Measuring instruments are the means by which this translation is made.

**Metrology** is the study of measurement.

A metric is a standard for measurement. The quantification of phenomena through the process of measurement relies on the existence of an explicit or implicit metric, which is the standard to which the measure is referenced. If I say I am '5', I am indicating a measurement without conveying an applicable standard. I may mean I am 5 years old, 5 feet high, or 5-time world raquetball champion.

Measuring physical quantities accurately is important in science, engineering and commerce.

For example, the unit for length might be a well-known person's foot, and the length of a boat can be given as the number of times that person's foot would fit the length of the boat.

Laws to regulate measurement were originally developed to prevent fraud. However, units of measurement are now generally defined on a scientific basis, and are established by international treaties.

The history of measurements is a topic within the History of Science and Technology. The meter was standardized as the unit for length after the French revolution, and has since been adopted throughout most of the world. The United States and the UK are in the process of converting to the SI system. This process is known as metrication.

Systems of measurement:

- Imperial units
- SI system, also known as the metric system
- Chinese units

Some important physical quantities include:

- the speed of light
- the fine-structure constant
- the charge of an electron

In economics, a unit of account is a basis for measuring a market.

See also:

- Weights and measures
- Historical weights and measures
- Timeline of time measurement technology
- Timeline of temperature and pressure measurement technology
- Dimensional analysis
- Dimensionless number
- conversion of units
- orders of magnitude
- league

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