A “number” is a mental symbol that integrates units into a single larger unit (or subdivides a unit into fractions) with reference to the basic number of “one,” which is the basic mental symbol of “unit.” Thus “5” stands for |||||. (Metaphysically, the referents of “5” are any five existents of a specified kind; epistemologically, they are represented by a single symbol.)

“The Cognitive Role of Concepts”
Introduction to Objectivist Epistemology, 63
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