one-to-one

one-to-one (comparative more one-to-one, superlative most one-to-one)

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 Britain) Involving direct communication between two people. Used especially to refer to situations in which one person is teaching one other person.
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.

• (involving direct communication): one-on-one (North America)

• one-to-many, many-to-one, many-to-many
• onto

• face-to-face
• man-to-man

one-to-one (plural one-to-ones)

1. A personal relationship between two people.

• (personal relationship between two people): 121, 1-2-1