The Collaborative International Dictionary of English v.0.48:

Concentration \Con`cen*tra"tion\, n. [Cf. F. concentration.]
   1. The act or process of concentrating; the process of
      becoming concentrated, or the state of being concentrated;
      concentration.
      [1913 Webster]

            Concentration of the lunar beams.     --Boyle.
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            Intense concetration of thought.      --Sir J.
                                                  Herschel.
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   2. The act or process of reducing the volume of a liquid, as
      by evaporation.
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            The acid acquires a higher degree of concentration.
                                                  --Knight.
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   3. (Metal.) The act or process of removing the dress of ore
      and of reducing the valuable part to smaller compass, as
      by currents of air or water.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dephlegmation \De`phleg*ma"tion\, n. [Cf. F. d['e]flegmation.]
   (Chem.)
   The operation of separating water from spirits and acids, by
   evaporation or repeated distillation; -- called also
   concentration, especially when acids are the subject of it.
   [Obs.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

concentration
    n 1: the strength of a solution; number of molecules of a
         substance in a given volume
    2: the spatial property of being crowded together [syn:
       concentration, density, denseness, tightness,
       compactness] [ant: dispersion, distribution]
    3: strengthening the concentration (as of a solute in a mixture)
       by removing diluting material [ant: dilution]
    4: increase in density
    5: complete attention; intense mental effort [syn:
       concentration, engrossment, absorption, immersion]
    6: bringing together military forces
    7: great and constant diligence and attention [syn: assiduity,
       assiduousness, concentration]