The Collaborative International Dictionary of English v.0.48:

Correspondence \Cor`re*spond"ence\ (-sp?nd"ens), n. [Cf. F.
   correspondance.]
   1. Friendly intercourse; reciprocal exchange of civilities;
      especially, intercourse between persons by means of
      letters.
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            Holding also good correspondence with the other
            great men in the state.               --Bacon.
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            To facilitate correspondence between one part of
            London and another, was not originally one of the
            objects of the post office.           --Macaulay.
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   2. The letters which pass between correspondents.
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   3. Mutual adaptation, relation, or agreement, of one thing to
      another; agreement; congruity; fitness; relation.
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WordNet (r) 3.0 (2006):

correspondence
    n 1: communication by the exchange of letters
    2: compatibility of observations; "there was no agreement
       between theory and measurement"; "the results of two tests
       were in correspondence" [syn: agreement, correspondence]
    3: the relation of corresponding in degree or size or amount
       [syn: commensurateness, correspondence,
       proportionateness]
    4: (mathematics) an attribute of a shape or relation; exact
       reflection of form on opposite sides of a dividing line or
       plane [syn: symmetry, symmetricalness, correspondence,
       balance] [ant: asymmetry, dissymmetry, imbalance]
    5: similarity by virtue of corresponding [syn: parallelism,
       correspondence]