n.
 (pl. affinities)
  - a spontaneous or natural liking or sympathy. 
▸a close relationship based on a common origin or structure.
 ▸relationship by marriage.
 - chiefly Biochemistry  the degree to which a substance tends to combine with another.
 
 
  Etymology
  ME: via OFr. from L. affinitas, from affinis ‘related’ (lit. ‘bordering on’).