Measures are the building blocks of metrics. They provide companies with the raw data they need to recognize successes and understand challenges.

Several systems of measurement have existed throughout history. The scientific study of measurements is called metrology. The concept of measure is also used in mathematics. Measures can be negative, which leads to a concept known as a signed measure.

## Quantity

A measure is a characteristic of an object, event or situation, used as a factor in expressing quantities of that entity. Examples include the length, weight or force of an object; the volume and capacity of a vessel or container; or the number of units sold of a particular product.

In physics, measures are non-negative extensive properties conserved over a space (or more precisely over a finite set of objects), or their linear combinations. The limiting case of these forms is the positive measure. Negative values lead to signed measures, and generalizations such as the Liouville measure on a symplectic manifold are useful in Hamiltonian and classical statistical mechanics.

In the business world, measures rely more on inputs such as resources allocated and activities performed, while metrics track progress toward desired results based on those inputs. The term metric also refers to an aggregation of measures, such as a key metric. See definition of metrics for further information.

## Time

Time is a universal and fundamental quantity which can be measured in a number of ways. Accurate time measurement is essential for modern society, from telecommunications to GPS satellite navigation.

There are two basic types of time measurements: epochs, which specify an instant in time, and time intervals, which measure the duration of continued events. Most methods of time measurement use phenomena that repeat regularly, such as the daily cycle of day and night or the periodic motion of the bob of a free-swinging pendulum.

Several different specifications of time have been used, including those based on the apparent movement of the sun across the sky and the moon’s phases, and the more accurate atomic clocks invented in 1955. The most widely accepted is Coordinated Universal Time (UTC), which replaces earlier astronomical and calendar time standards such as sidereal time, ephemeris time, and leap seconds. Other scales, such as Terrestrial Dynamical Time and Barycentric Coordinate Time, are used mainly in scientific contexts.

## Space

Space measurements are used to determine the distances between objects. They are necessary because the units we use for measurement on Earth are not large enough to measure the vast distances in the Universe. For example, it would be impossible to describe the distance from the Earth to the Sun using kilometres as the unit of measure. Instead, the light year is used.

Each panel ranked the priorities of a wide range of existing and proposed space-based measurement approaches and missions. They also considered the implications of the science objectives for global change and the continuity requirements that must be met by the measurements.

## Relationships

Measurement is a fundamental part of modern science; it is also important in engineering, commerce and daily life. As such, the elements, conditions, limitations and theoretical foundations of measurement have been much studied.

A measurement is a comparison of an unknown quantity with some known quantity that has been calibrated to suit the measuring system. It may involve the use of a standard artifact (such as a metronome) or it may be based on comparisons with objects that have been characterized and fixed in quantity, such as the seven base units of the International System of Units.

Mathematical theories of measurement, such as representational theory, concern the relations that numbers (and other mathematical entities) have with things that are not numbers. For example, 60 is twice 30, but this relation does not always reflect relations among objects. For this reason, representational theory requires some assumptions about the nature of the relationships that can be measured.