one-to-one
UK[ˌwʌn tə ˈwʌn]US[ˌwʌn tə ˈwʌn]
adj
Involving two people or things that directly correspond with each other
adj
(of a meeting or conversation) involving two people only
n
A relationship or correspondence in which each member of one set is linked to only one member of another set
Etymology
The phrase "one-to-one" is a modern English compound, originating in the late 19th to early 20th century. It is built from the Old English word "ān" (meaning one, single, alone) and the preposition "to", which derives from Old English "tō", indicating direction, relation, or correspondence. The logic of the phrase is transparently literal: it directly maps the concept of a single entity being directed toward or matched with another single entity. This literal sense evolved into the modern abstract meanings describing exact correspondence, private interaction, or mathematical mapping between individual elements of two sets.
Analysis
This is a compound phrase formed from the English numeral "one" and the preposition "to". It functions as a fixed idiomatic unit.
Examples
The tutor provides one-to-one instruction tailored to each student's needs.
There is a one-to-one correspondence between the points on the two lines.
The manager requested a one-to-one meeting to discuss the feedback privately.