Definitions:

1. a close connection marked by community of interests or similarity in nature or character noun
   • found a natural affinity with the immigrants
2. a natural attraction or feeling of kinship noun
   • an affinity for politics
3. in biology, state of relationship between organisms or groups of organisms resulting in resemblance in structure or structural parts noun
   • In anatomical structure, prehistoric hominids show close affinity with modern humans.
4. the force attracting atoms to each other and binding them together in a molecule noun
   • basic dyes have an affinity for wool and silk

Synonyms:

• chemical attraction
• kinship