lock and key
Proposed by a contributor, not yet supported by evidence.
Meaning · English
Two things that fit perfectly together
Literally: a lock and its key
Where it’s used:
Used
Widespread English
Sources & notes
Listed on Wikipedia “Irreversible binomial” (CC BY-SA 4.0, retrieved 2026-07-29). Definition drafted by AI (@cf/meta/llama-3.3-70b-instruct-fp8-fast) and auto-approved by rule on 2026-07-30; pending editor spot-check.
Common questions
What does “lock and key” mean?
Two things that fit perfectly together Literally: a lock and its key
Is “lock and key” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.