affinity

noun

Etymology: From Middle English affinite, from Old French affinité. Ostensibly equivalent to affine + -ity. See also af-.

1. A natural attraction or feeling of kinship to a person or thing.
2. A family relationship through marriage of a relative (e.g. sister-in-law), as opposed to consanguinity (e.g. sister).
3. A kinsman or kinswoman of a such relationship; one who is affinal.
4. The fact of and manner in which something is related to another.

   “There are, of course, certain differences of detail; for example, the placing of the safety valves on the boiler barrel behind the dome, which follows the practice in the Riddles 2-8-0 and 2-10-0 locomotives for the Ministry of Supply; but taken all in all, Britannia's boiler has a closer affinity with the Doncaster designs than with any other.”

   “A “signature” was placed on all things by God to indicate their affinities — but it was hidden, hence the search for arcane knowledge. Knowing was guessing and interpreting, not observing or demonstrating.”

5. Any romantic relationship.
6. A love interest; a paramour.

   “"Cut it short, sis, cut it short," he would growl at her if she started to murmur sweet "coo-coos" to her affinity stationed on the other end of the wire.”

7. Any passionate love for something.
8. Resemblances between biological populations, suggesting that they have a common origin, type or stock.
9. Structural resemblances between minerals; resemblances that suggest that they are of a common origin or type.
10. An attractive force between atoms, or groups of atoms, that contributes towards their forming bonds.
11. The attraction between an antibody and an antigen
12. A tendency to keep a task running on the same processor in a symmetric multiprocessing operating system to reduce the frequency of cache misses.
13. An automorphism of affine space.