If you get along with someone very well, you have an affinity with them. Sometimes opposites attract, so you might feel a strange affinity to someone who is seemingly very different from you.

When you are attracted to someone or something a great deal, we say that you have an affinity, a natural connection. Likewise, scientists use affinity to describe organisms that are alike or resemble each other. Interestingly, the Middle English word, affinite, originally applied to people who were connected or related by marriage, rather than by biology.

Definitions of affinity

n a natural attraction or feeling of kinship

“an affinity for politics”
“the mysterious affinity between them”
“James's affinity with Sam”
Type of:
attraction, attractiveness
the quality of arousing interest; being attractive or something that attracts

n a close connection marked by community of interests or similarity in nature or character

“found a natural affinity with the immigrants”
rapport, resonance
a relationship of mutual understanding or trust and agreement between people
a relation of affinity or harmony between people; whatever affects one correspondingly affects the other
mutual affection, mutual understanding
sympathy of each person for the other
Type of:
an abstraction belonging to or characteristic of two entities or parts together

n (anthropology) kinship by marriage or adoption; not a blood relationship

blood kinship, cognation, consanguinity
(anthropology) related by blood
a family relationship by virtue of remarriage
Type of:
family relationship, kinship, relationship
(anthropology) relatedness or connection by blood or marriage or adoption

n (biology) state of relationship between organisms or groups of organisms resulting in resemblance in structure or structural parts

“in anatomical structure prehistoric man shows close affinity with modern humans”
phylogenetic relation
Type of:
family relationship, kinship, relationship
(anthropology) relatedness or connection by blood or marriage or adoption

n inherent resemblance between persons or things

Type of:
similarity in appearance or external or superficial details

n the force attracting atoms to each other and binding them together in a molecule

“basic dyes have an affinity for wool and silk”
chemical attraction
Type of:
(physics) the influence that produces a change in a physical quantity

n (immunology) the attraction between an antigen and an antibody

Type of:
attraction, attractive force
the force by which one object attracts another