The Collaborative International Dictionary of English v.0.48:

Affinity \Af*fin"i*ty\, n.; pl. Affinities. [OF. afinit['e],
   F. affinit['e], L. affinites, fr. affinis. See Affined.]
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   1. Relationship by marriage (as between a husband and his
      wife's blood relations, or between a wife and her
      husband's blood relations); -- in contradistinction to
      consanguinity, or relationship by blood; -- followed by
      with, to, or between.
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            Solomon made affinity with Pharaoh.   --1 Kings iii.
                                                  1.
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   2. Kinship generally; close agreement; relation; conformity;
      resemblance; connection; as, the affinity of sounds, of
      colors, or of languages.
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            There is a close affinity between imposture and
            credulity.                            --Sir G. C.
                                                  Lewis.
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   2. Companionship; acquaintance. [Obs.]
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            About forty years past, I began a happy affinity
            with William Cranmer.                 --Burton.
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   4. (Chem.) That attraction which takes place, at an
      insensible distance, between the heterogeneous particles
      of bodies, and unites them to form chemical compounds;
      chemism; chemical or elective affinity or attraction.
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   5. (Nat. Hist.) A relation between species or higher groups
      dependent on resemblance in the whole plan of structure,
      and indicating community of origin.
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   6. (Spiritualism) A superior spiritual relationship or
      attraction held to exist sometimes between persons, esp.
      persons of the opposite sex; also, the man or woman who
      exerts such psychical or spiritual attraction.
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