- A natural attraction, liking, or feeling of kinship.
- Relationship by marriage.
- An inherent similarity between persons or things. See synonyms at likeness.
- Biology. A relationship or resemblance in structure between species that suggests a common origin.
- Immunology. The attraction between an antigen and an antibody.
- Chemistry. An attraction or force between particles that causes them to combine.
[Middle English affinite, from Old French afinite, from Latin affīnitās, from affīnis, related by marriage. See affined.]
USAGE NOTE In the sense of "attraction," affinity may be followed by of, between, or with. Thus one may speak of the close affinity of James and Samuel, or of the affinity between James and Samuel, or of James's affinity with Samuel. In its chemical use affinity is generally followed by for: a dye with an affinity for synthetic fabrics. • One might want to avoid using affinity as a simple synonym for liking since 62 percent of the Usage Panel rejects the example Her affinity for living in California led her to reject a chance to return to New York. Nevertheless, the more sophisticated tone inherent in this use of the word can lend an archness to certain contexts, as when Barbara Tuchman writes of Kaiser Wilhelm's "affinity for coarse physical jokes practiced upon his courtiers." This may be why 65 percent of the Usage Panel approved of this quotation when it was presented as an example.
