O2

from The Collaborative International Dictionary of English v.0.48

Chromophore \Chro"mo*phore\, n. [Gr. ? color + fe`rein to bear.]
   (Chem.)
   Any chemical group or residue (as {NO2}; {N2}; or {O2}) which
   imparts some decided color to the compound of which it is an
   ingredient.
   [1913 Webster]

from The Free On-line Dictionary of Computing (8 July 2008)

O2

   Object-Oriented.  {Object-oriented database} language used in
   the {Altair} project.  Implemented as an {interpreter}.  GIP
   Altair, Versailles, France.  Francois Bancilhon et al, in
   Advances in Object-Oriented Database Systems, K.R. Dittrich
   ed, LNCS 334, Springer 1988.  See {CO2}.

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