An Etymological Dictionary of Astronomy and Astrophysics

A prefix occurring in loanwords from L. to indicate:

1. Opposition, reversal: decentralize, decode, deactivate, de-emphasis.
   
2. Removal from: dethrone.
   
3. Reduction, degradation: declass, devalue.
   
4. reversal: detract, detect.
   
5. Derivation from: derive, deverbative.

Etymology (EN): M.E., from O.Fr. de-, des-, partly from L. de- “from, down, away,” and partly from L. → dis-.

Etymology (PE): Prefix vâ- denoting “reversal, opposition; separation; repetition; open; off; away,” variant of bâz-, from Mid.Pers. abâz-, apâc-; O.Pers. apa- [pref.] “away, from;” Av. apa- [pref.] “away, from,”
apaš [adv.] “toward the back;” cf. Skt. ápāñc “situated behind.”
Foru- “down, downward; below; beneath,” Mid.Pers. frôt “down, downward,” O.Pers. fravata “forward, downward,” Skt. pravát- “a sloping path, the slope of a mountain.”