- b (1) : an attraction to or liking for something <people with an affinity to darkness — Mark Twain> <pork and fennel have a natural affinity for each other — Abby Mandel> (2) : an attractive force between substances or particles that causes them to enter into and remain in chemical combination
- c : a person especially of the opposite sex having a particular attraction for one
- 3a : likeness based on relationship or causal connection <found an affinity between the teller of a tale and the craftsman — Mary McCarthy> <this investigation, with affinities to a case history, a psychoanalysis, a detective story — Oliver Sacks>
- b : a relation between biological groups involving resemblance in structural plan and indicating a common origin
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 bears to the kindred of the other. In English, affinity is usually signified by adding "-in-law" to the degree of kinship. In addition to kinship by marriage, "affinity" can sometimes also include kinship by adoption.
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. It differs from affinity in law and canon law which generally refer to the marriage relationship. Social affinity is generally thought of as "marriage" to ideas, ideals and causes shared by a tight community of people.
Affinity in taxonomy – mainly in life sciences or natural history – refers to resemblance suggesting a common descent, phylogenetic relationship, or type. The term does, however, have broader application, such as in geology (for example, in descriptive and theoretical works, and similarly in astronomy (for example, see "Centaur object" in the context of 2060 Chiron's close affinity with icy comet nuclei.
In chemical physics and physical chemistry, chemical affinity is the electronic property by which dissimilar chemical species are capable of forming chemical compounds. Chemical affinity can also refer to the tendency of an atom or compound to combine by chemical reaction with atoms or compounds of unlike composition.