Rare math symbol from Leibniz-era notation, used to mean two quantities have no common measure, the opposite of commensurability.
U+1DB0CCOMMENSURABILITYU+1DB0ECOMMENSURABILITY IN SQUAREU+1DB0BTWO-LINE LESS-THANU+1DB0FINCOMMENSURABILITY IN SQUAREU+1DB0ATWO-LINE GREATER-THANU+1DB10CARTESIAN EQUALS SIGNU+1DB09INVERTED SQUARE RIGHT OPEN BOX OPERATORU+1DB11LEIBNIZIAN CONGRUENCEU+1DB08INVERTED SQUARE LEFT OPEN BOX OPERATORU+1DB12LEIBNIZIAN CONGRUENCE WITH VERTICAL BARU+1DB07LEIBNIZIAN GREATER-THAN OR LESS-THANU+1DB13LEIBNIZIAN CONGRUENCE-229 characters in the Miscellaneous Symbols and Arrows Extended Unicode block.
U+1DB00LEIBNIZIAN EQUALS SIGNU+1DB01LEIBNIZIAN EQUALS SIGN WITH DOUBLE VERTICALSU+1DB02LEIBNIZIAN EQUALS SIGN WITH SMALL SU+1DB03LEIBNIZIAN GREATER-THANU+1DB04LEIBNIZIAN LESS-THANU+1DB05LEIBNIZIAN GREATER-THAN WITH SMALL PU+1DB06LEIBNIZIAN LESS-THAN WITH SMALL PU+1DB07LEIBNIZIAN GREATER-THAN OR LESS-THANU+1DB08INVERTED SQUARE LEFT OPEN BOX OPERATORU+1DB09INVERTED SQUARE RIGHT OPEN BOX OPERATORU+1DB0ATWO-LINE GREATER-THANU+1DB0BTWO-LINE LESS-THANU+1DB0CCOMMENSURABILITYU+1DB0DINCOMMENSURABILITYU+1DB0ECOMMENSURABILITY IN SQUAREU+1DB0FINCOMMENSURABILITY IN SQUAREU+1DB10CARTESIAN EQUALS SIGNU+1DB11LEIBNIZIAN CONGRUENCEU+1DB12LEIBNIZIAN CONGRUENCE WITH VERTICAL BARU+1DB13LEIBNIZIAN CONGRUENCE-2U+1DB14LEIBNIZIAN CONGRUENCE-2 INVERTEDU+1DB15LEIBNIZIAN CONGRUENCE-2 WITH HORIZONTAL BARU+1DB16LEIBNIZIAN CONGRUENCE-2 WITH HORIZONTAL AND VERTICAL BARU+1DB17LEIBNIZIAN COINCIDENCEU+1DB18INVERTED LAZY S OVER LAZY SU+1DB19LEIBNIZIAN SIMILARITYU+1DB1ALEIBNIZIAN SIMILARITY-2U+1DB1BLEIBNIZIAN DISSIMILARITYU+1DB1CFACIT SYMBOL