separatrix (|)
Definition - An obsolete name for the | symbol.

1. This symbol was once used to perform the function that is now performed by the decimal point (e.g. 2|3 = 2.3).

Etymology -
The word derives from the Late Latin separare, to separate.

Oxford English Dictionary -
Its first citation is from 1660:
"But the best and most distinct way of distinguishing them [sc. Decimals] is by a rectangular line after the place of the unit, called Seperatrix. …. [Ibid. 13] Therefore in writing of decimal parts let the seperatrix be always used."
(J. Moore Arith. 11 )

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