affinity af·fin·i·ty (ə-fĭn'ĭ-tē)
An attraction or force between particles that causes them to combine.
The attraction between an antigen and an antibody.
A relationship or resemblance in structure between species that suggests a common origin.
The selective staining of a tissue by a dye. The selective uptake of a dye, chemical, or other substance by a tissue.