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Numbers are mathematical entities that originally came into use to satisfy a need to count objects and measure quantities. From tallying systems and counting numbers to integers, zero, rational numbers, irrational numbers, complex numbers and beyond, progressively broader sets of numbers came into use over time as the need for more general numeric entities arose. Use Wolfram|Alpha's computational knowledge of these and other number sets and systems to identify their properties or to perform calculations in and across their respective domains.