Dimensionless numbers

The Richter magnitude scale (also Richter scale) assigns a magnitude number to quantify the size of an earthquake.

In physics, redshift happens when light or other electromagnetic radiation from an object is increased in wavelength, or shifted to the red end of the spectrum.

In electronics, gain is a measure of the ability of a two port circuit (often an amplifier) to increase the power or amplitude of a signal from the input to the output port by adding energy converted from some power supply to the signal.

The Beaufort scale /ˈboʊfərt/ is an empirical measure that relates wind speed to observed conditions at sea or on land.

Quantum numbers describe values of conserved quantities in the dynamics of a quantum system.

In physics, a gravitational coupling constant is a constant characterizing the gravitational attraction between a given pair of elementary particles.

The transmission coefficient is used in physics and electrical engineering when wave propagation in a medium containing discontinuities is considered.

Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material.

In physics and electrical engineering the reflection coefficient is a parameter that describes how much of an electromagnetic wave is reflected by an impedance discontinuity in the transmission medium.

In statistics, dependence or association is any statistical relationship, whether causal or not, between two random variables or two sets of data.

Total internal reflection is the phenomenon which occurs when a propagated wave strikes a medium boundary at an angle larger than a particular with respect to the normal to the surface.

In mathematics, two quantities are in the silver ratio (also silver mean or silver constant) if the ratio of the sum of the smaller and twice the larger of those quantities, to the larger quantity, is the same as the ratio of the larger one to the smaller one (see below).

In optics, the refractive index or index of refraction n of a material is a dimensionless number that describes how light propagates through that medium.

In mathematics, the trigonometric functions (also called the circular functions) are functions of an angle.

In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without being scattered.

Signal-to-noise ratio (abbreviated SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise.

In thermal physics and thermodynamics, the heat capacity ratio or adiabatic index or ratio of specific heats or Poisson constant, is the ratio of the heat capacity at constant pressure (CP) to heat capacity at constant volume (CV).

The Lorentz factor or Lorentz term is the factor by which time, length, and relativistic mass change for an object while that object is moving.