An Affinity

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). Affinity (law) - Wikipedia Affinity (Catholic canon law) - Wikipedia
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.
5. Any romantic relationship. Affinity (sociology) - Wikipedia
6. Any passionate love for something.
7. (taxonomy) resemblances between biological populations, suggesting that they have a common origin, type or stock. Affinity (taxonomy) - Wikipedia
8. (geology) structural resemblances between minerals; resemblances that suggest that they are of a common origin or type.
9. (chemistry) An attractive force between atoms, or groups of atoms, that contributes towards their forming bonds Chemical affinity - Wikipedia
10. (medicine) The attraction between an antibody and an antigen
11. (computing) tendency to keep a task running on the same processor in a symmetric multiprocessing operating system to reduce the frequency of cache misses
12. (geometry) An automorphism of affine space.