separatrix

English

Etymology

Learned borrowing from Latin sēparātrīx, the feminine form of separator (originally owing to an implied līnea (line)), from sēparāre (to divide; to separate) + -trix (forming female agents). By surface analysis, separate +‎ -trix. First developed as a decimal mark among the medieval Arab mathematicians, whence a shorter variant gave rise to the decimal comma employed by many European countries and their former colonies.

Pronunciation

  • IPA(key): /sɛpəˈɹeɪtɹɪks/
  • Rhymes: -eɪtɹɪks

Noun

separatrix (plural separatrixes or separatrices)

  1. (typography, historical) The ⟨L⟩ or pipe|mark formerly used to divide integers from decimals.
    Synonyms: pipe, slash
    Hypernyms: decimal mark < radix point < point, mark, character, separator
    Coordinate terms: decimal point (precise sense), decimal comma
    • 1660, Jonas Moore, Moor's Arithmetick, page 13:
      Therefore in writing of decimall parts let the separatrix be always used.
  2. (typography, obsolete) Synonym of decimal point, which replaced such marks.
  3. (typography) The proofreader's mark resembling a slash ⟨ / ⟩ or vertical bar ⟨ | ⟩ placed after a note in the margin to indicate that it should replace the item(s) struckthrough in the running text or to separate it from other margin notes.
  4. A terminator: a line on a partially-illuminated surface separating the lit and shaded regions.
  5. (physics) The line between regions having different magnetic fields.
  6. (mathematics) The boundary separating two modes of behavior in a differential equation.

Further reading