### dex

**(order-of-magnitude, decimal exponent)**
(a number or ratio's log base 10)

The term **dex** (for **decimal exponent**) refers to the exponent
of a number in **scientific notation**, and has come to be used
like a unit that specifies a number's **order-of-magnitude**.
For example, 100 could be described as 2 dex,
or two numbers that differ by a factor of
1000 could be said to differ by 3 dex.
As such a unit, a *dex* is sometimes cited as a fraction
(making it the value's more-precise log base 10)
whereas a cited *order-of-magnitude* is commonly rounded to an integer.
Within physics and astrophysics, the term *dex* is sometimes used,
but *order-of-magnitude* is probably used more.
A common circumstance is describing the ratio of two numbers by
the ratio's dex or order-of-magnitude.
Example of the *dex* in scientific notation:

2.40×10^{7}

This number's *dex* as specified is 7 and the number could be described
as "7 dex" or "having an order-of-magnitude of 7". It could also
be described as "7.38 dex", which is the number's log base 10
not rounded to an integer.
Example of a ratio as a dex: "Jupiter's and Earth's masses
differ by 2.5 dex" (i.e., log_{10} of 318, their ratio).

(*mathematics,terminology,unit*)
**Further reading:**

http://en.wiktionary.org/wiki/dex

https://joe-antognini.github.io/astronomy/what-is-a-dex

http://www.physics.unlv.edu/~jeffery/astro/logarithm/logarithm.html

https://astronomy.stackexchange.com/questions/17911/understanding-dex

**Referenced by pages:**

axion (A^{0})

back-of-the-envelope calculation

barrier

CMB Stage-4 (CMB-S4)

cosmic dust

dark energy

dense core mass function (DCMF)

event horizon (EH)

exascale computing

free-fall time

fuzzy dark matter (FDM)

H-R diagram (HRD)

hyperfine structure

inflation

ionizing radiation

jansky (Jy)

Kelvin-Helmholtz timescale (KH timescale)

main-sequence lifetime (MS lifetime)

N-body problem

numerical analysis

planet formation

parts per million (PPM)

projected separation

SI

superluminous supernova (SLSN)

speed of light (c)

stellar dynamics

task-based parallelism (TBP)

time standard

valley of beta stability

Index