cross-ratio

noun

A special number associated with an ordered quadruple of collinear points, particularly points on a projective line, and preserved by the fractional linear transformations.

Similar
anharmonic ratiodouble ratio
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Meanings

nouncross-ratio (plural cross-ratios)

plural cross-ratios · alternative crossratio

  1. geometryA special number associated with an ordered quadruple of collinear points, particularly points on a projective line, and preserved by the fractional linear transformations.

    Synonyms: anharmonic ratio, double ratio

Synonyms & antonyms

nounA special number associated with an ordered quadruple of collinear points, particularly points on a projective line, and preserved by the fractional linear transformations.

Similar
anharmonic ratiodouble ratio

Origin

From cross- + ratio.

Full word history & related roots →

Translations

French birapport
  • birapporta special number associated with an ordered quadruple of collinear points, particularly points on a projective line, and preserved by the fractional linear transformations
Cite this entry
APA

cross-ratio. (n.d.). In WatkinsX Dictionary. Retrieved November 3, 2026, from https://dictionary.watkinsx.com/word/cross-ratio

MLA

“cross-ratio.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/cross-ratio. Accessed November 3, 2026.

Chicago

WatkinsX Dictionary, s.v. “cross-ratio,” accessed November 3, 2026, https://dictionary.watkinsx.com/word/cross-ratio.

Source: cross-ratio on Wiktionary, CC BY-SA 4.0.