separatrix

Meaning

Noun

• The ⟨L⟩ or pipe ⟨''⟩ mark formerly used to divide integers from decimals.
• Synonym of decimal point, which replaced such marks.
• 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.
• A terminator: a line on a partially-illuminated surface separating the lit and shaded regions.
• The line between regions having different magnetic fields.
• The boundary separating two modes of behavior in a differential equation.

Origin

• Borrowed from Latin separatrix, the feminine form of separator (originally owing to an implied līnea), from separo + -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.