Definition of "one-to-one" in English

adjective

1. Matching each member of one set with exactly one member of another set.

   • There is a one-to-one relationship between days with large cash shortages and his workdays.

2. (chiefly UK) Involving direct communication between two people.

   • a one-to-one discussion
   • a one-to-one teaching session

3. (mathematics, of a function) Injective, being an injection: having the property that no two elements of the domain are mapped to the same image.

noun

1. A personal relationship between two people.

2. A direct match or equivalent.