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Basic reproduction number: number of infections caused on average by an infectious individual over entire infectious period: epidemiology: Body fat percentage: total mass of fat divided by total body mass, multiplied by 100: biology Kt/V: Kt/V: medicine (hemodialysis and peritoneal dialysis treatment; dimensionless time) Waist–hip ratio
A pendulum with a period of 2.8 s and a frequency of 0.36 Hz. For cyclical phenomena such as oscillations, waves, or for examples of simple harmonic motion, the term frequency is defined as the number of cycles or repetitions per unit of time.
The number one is recognized as a dimensionless base quantity. [4] Radians serve as dimensionless units for angular measurements, derived from the universal ratio of 2π times the radius of a circle being equal to its circumference. [5]
The Keulegan–Carpenter number is important for the computation of the wave forces on offshore platforms. In fluid dynamics , the Keulegan–Carpenter number , also called the period number , is a dimensionless quantity describing the relative importance of the drag forces over inertia forces for bluff objects in an oscillatory fluid flow .
Dimensionless numbers (or characteristic numbers) have an important role in analyzing the behavior of fluids and their flow as well as in other transport phenomena. [1] They include the Reynolds and the Mach numbers, which describe as ratios the relative magnitude of fluid and physical system characteristics, such as density, viscosity, speed of sound, and flow speed.
In the physical sciences, the wavenumber (or wave number), also known as repetency, [1] is the spatial frequency of a wave. Ordinary wavenumber is defined as the number of wave cycles divided by length; it is a physical quantity with dimension of reciprocal length , expressed in SI units of cycles per metre or reciprocal metre (m −1 ).
These include the Boltzmann constant, which gives the correspondence of the dimension temperature to the dimension of energy per degree of freedom, and the Avogadro constant, which gives the correspondence of the dimension of amount of substance with the dimension of count of entities (the latter formally regarded in the SI as being dimensionless).
It is a dimensionless quantity (dimensionless physical constant), independent of the system of units used, which is related to the strength of the coupling of an elementary charge e with the electromagnetic field, by the formula 4πε 0 ħcα = e 2.