affinity

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