The Collaborative International Dictionary of English v.0.48:

Cognizance \Cog"ni*zance\ (? or ?; 277), n. [OF. conissance,
   conoissance, F. connaissance, LL. cognoscentia, fr. L.
   cognoscere to know. See Cognition, and cf. Cognoscence,
   Connoisseur.]
   1. Apprehension by the understanding; perception;
      observation.
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            Within the cognizance and lying under the control of
            their divine Governor.                --Bp. Hurd
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   2. Recollection; recognition.
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            Who, soon as on that knight his eye did glance,
            Eftsoones of him had perfect cognizance. --Spenser.
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   3. (Law)
      (a) Jurisdiction, or the power given by law to hear and
          decide controversies.
      (b) The hearing a matter judicially.
      (c) An acknowledgment of a fine of lands and tenements or
          confession of a thing done. [Eng.]
      (d) A form of defense in the action of replevin, by which
          the defendant insists that the goods were lawfully
          taken, as a distress, by defendant, acting as servant
          for another. [Eng.] --Cowell. Mozley & W.
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   4. The distinguishing mark worn by an armed knight, usually
      upon the helmet, and by his retainers and followers:
      Hence, in general, a badge worn by a retainer or
      dependent, to indicate the person or party to which he
      belonged; a token by which a thing may be known.
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            Wearing the liveries and cognizance of their master.
                                                  --Prescott.
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            This pale and angry rose,
            As cognizance of my blood-drinking hate. --Shak.
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WordNet (r) 3.0 (2006):

cognizance
    n 1: having knowledge of; "he had no awareness of his mistakes";
         "his sudden consciousness of the problem he faced"; "their
         intelligence and general knowingness was impressive" [syn:
         awareness, consciousness, cognizance, cognisance,
         knowingness] [ant: incognizance]
    2: range of what one can know or understand; "beyond my ken"
       [syn: cognizance, ken]
    3: range or scope of what is perceived

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "cognizance":
   acknowledgment, apperception, appreciation, appreciativeness,
   attention, awareness, benediction, cognition, consciousness,
   credit, crediting, due, grace, heed, hymn, insight, knowledge,
   mark, mind, mindfulness, noesis, note, notice, observance,
   observation, paean, perception, praise, prayer of thanks,
   realization, recognition, regard, remark, right, sensibility,
   thank offering, thank-you, thanks, thanksgiving, what is owing