■ noun ( plural affinities )
1》 a spontaneous or natural liking or sympathy.
↘a close relationship based on a common origin or structure.
↘relationship by marriage.
2》 chiefly Biochemistry the degree to which a substance tends to combine with another.
Origin
ME: via OFr. from L. affinitas , from affinis 'related' (lit. 'bordering on').