1. a natural liking for or attraction to a person, thing, idea, etc.
2. a person, thing, idea, etc., for which such a natural liking or attraction is felt.
3. relationship by marriage or by ties other than those of blood ( distinguished from consanguinity).
4. inherent likeness or agreement; close resemblance or connection.
5. Biology . the phylogenetic relationship between two organisms or groups of organisms resulting in a resemblance in general plan or structure, or in the essential structural parts.
7. of or pertaining to persons who share the same interests: to arrange charter flights for opera lovers and other affinity groups.