affinity

 
Pronunciation: /əˈfɪnɪti/

noun (plural affinities)

  • 1a natural liking for and understanding of someone or something: he had a special affinity with horses
  • a similarity of characteristics suggesting a relationship, especially a resemblance in structure between animals, plants, or languages: a semantic affinity between two words
  • [mass noun] relationship, especially by marriage as opposed to blood ties: the distinction between kinship and affinity is not always clear-cut
  • 2chiefly Biochemistry the degree to which a substance tends to combine with another: the bacterial proteins bind to these molecules with high affinity

Origin:

Middle English (in the sense 'relationship by marriage'): via Old French from Latin affinitas, from affinis 'related' (literally 'bordering on'), from ad- 'to' + finis 'border'