Infinity is an unbounded quantity greater than every real (and every whole) number.

Infinity, most often denoted as ∞, is an unbounded quantity that is greater than every real number. The symbol ∞ had been used as an alternative to M (1000) in Roman numerals until 1655, when John Wallis suggested it be used instead for infinity. Infinity is a very tricky concept to work with, as evidenced by some of the counterintuitive results that follow from Georg Cantor's treatment of infinite sets.

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Infinity

high school level (California mathematical analysis standard)