A personal relationship between two people.
Matching each member of one set with exactly one member of another set.
Injective, being an injection: having the property that no two elements of the domain are mapped to the same image.
Involving direct communication between two people.
A face-to-face meeting, or private conversation between two people, usually in an intimate setting; a head-to-head.
A bench or sofa that allows two people to talk face-to-face, especially one that is S-shaped.
A variety of early flowering, fragrant daffodil.
In private, between two people; head-to-head.