Rule of Three
Preserved but no longer current.
Meaning · English
The rule of simple proportion ; by which, given the relationship of two entities, the proportional relationship of a third can be ascertained.
Era: ca. 1898 (Victorian)
Sources & notes
Reproduced from Brewer’s Dictionary of Phrase and Fable (1898 edition, public domain; archive.org, retrieved 2026-07-31; OCR text, minor errors possible). Reflects the scholarship and attitudes of its era.
Common questions
What does “Rule of Three” mean?
The rule of simple proportion ; by which, given the relationship of two entities, the proportional relationship of a third can be ascertained.
Is “Rule of Three” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.