Definitions of affinity on the Web:

• (immunology) the attraction between an antigen and an antibody
• (anthropology) kinship by marriage or adoption; not a blood relationship
• (biology) state of relationship between organisms or groups of organisms resulting in resemblance in structure or structural parts; "in anatomical structure prehistoric man shows close affinity with modern humans"
• a close connection marked by community of interests or similarity in nature or character; "found a natural affinity with the immigrants"; "felt a deep kinship with the other students"; "anthropology's kinship with the humanities"
• the force attracting atoms to each other and binding them together in a molecule; "basic dyes have an affinity for wool and silk"
• inherent resemblance between persons or things
• a natural attraction or feeling of kinship; "an affinity for politics"; "the mysterious affinity between them"; "James's affinity with Sam"
  wordnetweb.princeton.edu/perl/webwn

• is a tactical role-playing video game franchise developed by Intelligent Systems (specifically Shouzou Kaga), the maker of Advance Wars (which shares some of Fire Emblems strategic elements), and published by Nintendo. ...
  en.wikipedia.org/wiki/Affinity_(Fire_Emblem)

• In Canon law of the Catholic Church, affinity is a relationship arising from the sexual intercourse of a man and a woman, sufficient for the generation of children, whereby the man becomes related to the woman's blood-relatives and the woman to the man's.
  en.wikipedia.org/wiki/Affinity_(canon_law)

• Affinity in terms of sociology, refers to "kinship of spirit", interest and other interpersonal commonalities. Affinity is characterized by high levels of intimacy and sharing, usually in close groups, also known as affinity groups. ...
  en.wikipedia.org/wiki/Affinity_(sociology)

• Affinity is a 1999 historical fiction novel by Sarah Waters. It is the author's second novel, following Tipping the Velvet, and followed by Fingersmith.
  en.wikipedia.org/wiki/Affinity_(novel)

• Affinity is a 1962 album by the Oscar Peterson Trio.
  en.wikipedia.org/wiki/Affinity_(Oscar_Peterson_album)

• Affinity is an album by American jazz pianist Bill Evans, released in 1979.
  en.wikipedia.org/wiki/Affinity_(Bill_Evans_album)

• Affinity were an English jazz-rock fusion band, active from mid-1968 to January 1971.
  en.wikipedia.org/wiki/Affinity_(band)

• In law and in cultural anthropology, affinity, as distinguished from consanguinity, is kinship by marriage. It is the relation which each party to a marriage, the husband and wife, bears to the kindred of the other.
  en.wikipedia.org/wiki/Affinity_(law)