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Examples include number of particles and population size. In mathematics, the "number of elements" in a set is termed cardinality. Countable nouns is a related linguistics concept. Counting numbers, such as number of bits, can be compounded with units of frequency (inverse second) to derive units of count rate, such as bits per second.
Counts and proportions are technically dimensionless, and so have no units of measurement, although identifiers such as "people", "births", "infections" and the like are used for clarity. Rates of change are counts per unit of time and strictly have inverse time dimensions (per unit of time
digital imaging (smallest addressable unit) Power factor: pf = electrical (real power to apparent power) Power number: N p = fluid mechanics, power consumption by rotary agitators; resistance force versus inertia force) Prater number: β
There is no accepted theory explaining the value of α; Richard Feynman elaborates: There is a most profound and beautiful question associated with the observed coupling constant, e – the amplitude for a real electron to emit or absorb a real photon. It is a simple number that has been experimentally determined to be close to 0.08542455.
[b] Other useful derived quantities can be specified in terms of the SI base and derived units that have no named units in the SI, such as acceleration, which has the SI unit m/s 2. [1]: 139 A combination of base and derived units may be used to express a derived unit.
In physics, natural unit systems are measurement systems for which selected physical constants have been set to 1 through nondimensionalization of physical units.For example, the speed of light c may be set to 1, and it may then be omitted, equating mass and energy directly E = m rather than using c as a conversion factor in the typical mass–energy equivalence equation E = mc 2.
The atomic units have been chosen to use several constants relating to the electron: the electron mass, the elementary charge, the Coulomb constant and the reduced Planck constant. The unit of energy in this system is the total energy of the electron in the Bohr atom and called the Hartree energy. The unit of length is the Bohr radius.
Bahar – a unit of length in Iran, and was a unit of mass in Oman; Batman – mostly a unit of mass, but sometimes a unit of area; Demal – unit of concentration; Dimi (metric prefix) – a discontinued non-SI metric prefix for 10 −4 [7] Einstein – unit of energy, and a unit of amount of substance; Fanega – a unit of dry volume, and a ...