AmountOfSubstanceMeasure | **is a kind of** ConstantQuantity | |

ConstantQuantity | *documentation* A ConstantQuantity is a PhysicalQuantity which has a constant value, e.g. 3 meters *and* 5 hours. The magnitude (see *MagnitudeFn*) of every ConstantQuantity is a RealNumber. ConstantQuantities are distinguished from FunctionQuantities, which map ConstantQuantities to other ConstantQuantities. All ConstantQuantites are expressed with the BinaryFunction *MeasureFn*, which takes a Number *and* a UnitOfMeasure as arguments. For example, 3 Meters can be expressed as (*MeasureFn* 3 *Meter*). ConstantQuantities form a partial order (see PartialOrderingRelation) with the *lessThan* relation, since *lessThan* is a RelationExtendedToQuantities *and* *lessThan* is defined over the RealNumbers. The *lessThan* relation is *not* a total order (see TotalOrderingRelation) over the class ConstantQuantity since elements of some subclasses of ConstantQuantity (such as length quantities) are incomparable to elements of other subclasses of ConstantQuantity (such as mass quantities) | |

**has axiom** (=> (*instance* ?FUNCTION UnaryConstantFunctionQuantity) (*and* (*domain* ?FUNCTION 1 ConstantQuantity) (*range* ?FUNCTION ConstantQuantity)))
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**is first ***domain* of *MagnitudeFn* | |

**is second ***domain* of *measure* | |

PhysicalQuantity | **is partitioned into** ConstantQuantity, FunctionQuantity | |

Abstract | **is ***disjoint* from Physical | |