Editing Dimensionless quantity (section)

== List ==
{{Main|List of dimensionless quantities}}

=== Physics and engineering ===
* [[Lorentz factor]]<ref>{{Cite journal |last=Einstein |first=A. |date=2005-02-23 |title=Zur Elektrodynamik bewegter Körper [AdP 17, 891 (1905)] |url=https://onlinelibrary.wiley.com/doi/10.1002/andp.200590006 |journal=Annalen der Physik |language=en |volume=14 |issue=S1 |pages=194–224 |doi=10.1002/andp.200590006}}</ref> – parameter used in the context of special relativity for time dilation, length contraction, and relativistic effects between observers moving at different velocities
* [[Fresnel number]] – wavenumber (spatial frequency) over distance

* [[Beta (plasma physics)]] – ratio of plasma pressure to magnetic pressure, used in magnetospheric physics as well as fusion plasma physics.
* [[Thiele modulus]] – describes the relationship between diffusion and reaction rate in porous catalyst pellets with no mass transfer limitations.
* [[Numerical aperture]] – characterizes the range of angles over which the system can accept or emit light.
* Zukoski number, usually noted <math>Q^*</math>, is the ratio of the heat release rate of a fire to the enthalpy of the gas flow rate circulating through the fire. Accidental and natural fires usually have a <math>Q^* \approx 1</math>. Flat spread fires such as forest fires have <math>Q^*<1</math>. Fires originating from pressured vessels or pipes, with additional momentum caused by pressure, have <math>Q^*\gg 1</math>.<ref>{{cite web |url=https://authors.library.caltech.edu/21188/1/287_Zukoski_EE_1985.pdf |title=Fluid Dynamic Aspects of Room Fires |author-last=Zukoski |author-first=Edward E. |date=1986 |publisher=Fire Safety Science |access-date=2022-06-13}}</ref>

==== Fluid mechanics ====
{{Main|Dimensionless numbers in fluid mechanics}}

=== Chemistry ===
* [[Relative density]] – density relative to [[water]]
* [[Relative atomic mass]], [[Standard atomic weight]]
* [[Equilibrium constant]] (which is sometimes dimensionless)

=== Other fields ===
* [[Cost of transport]] is the [[efficiency]] in moving from one place to another
* [[Elasticity (economics)|Elasticity]] is the measurement of the proportional change of an economic variable in response to a change in another
* [[Basic reproduction number]] is a dimensionless ratio used in epidemiology to quantify the transmissibility of an infection.