D-

Etymology 1
From, old name of.

Prefix

 * 1)  one of two mirror-image forms of an isomer (enantiomer) derived from (R)-glyceraldehyde. Written in small caps.

Usage notes
The prefixes and  for enantiomers are not the same as lowercase  and  for levorotatory and dextrorotatory isomers, although there is substantial overlap in the physical chemistry (that is, sometimes they happen to coincide).

Etymology 2
From /. From SI metric system origins. From, from.

Etymology
From D-Day.

Prefix

 * 1) ... days before the big event.