dex

Etymology 1
Contraction of.

Noun

 * 1)  An order or factor of ten.
 * 2) * 2004, Cartledge et al 2004, The Homogeneity of Interstellar Oxygen in the Galactic Disk, Abstract, The Astrophysical Journal, Volume 613, Issue 2, pp. 1037-1048,
 * The data points for low- paths are scattered more widely than those for denser sight lines, because O/H ratios for such paths shorter than 800 pc are generally about 0.10 dex lower than the values for longer ones.

Usage notes
Used both to refer to the function $$\mathrm{dex}(x) = 10^x$$ and the number of (possibly fractional) orders of magnitude separating two numbers. $$\log_{10}(5) \approx 0.70$$ and $$\log_{10}(8) \approx 0.90$$, so the ratio of 8 to 5 is about 0.20 dex.

Etymology 2
By shortening.

Noun

 * 1)  Dexterity.

Etymology 3
Shortening of various drug names.

Noun

 * 1)  Dextromethorphan.
 * 2)  Dexamethasone.
 * 3)  Dextroamphetamine/dexedrine.

Noun

 * 1) river