arithmos

Arithmos, from the Greek word ἀριθμός, is the noun for number. In both ancient and modern Greek, arithmos denotes a quantity, a numeral, or a count, and it can refer to natural numbers or numbers in general. The term is the etymological source of several English mathematical terms, notably arithmetic, which comes from arithmētikē, the science or art of counting, and arithmetical, from arithmētikos, relating to numbers.

In classical Greek mathematics, arithmoi referred to numbers used in calculation and were treated as abstract objects within arithmetic and number theory. Greek mathematicians, including the Pythagoreans and Euclid, discussed arithmoi as the foundational elements of mathematical reasoning, distinguishing them from geometric quantities in the broader mathematical tradition of the time.

Today, arithmos remains the standard Modern Greek word for number. It is used in everyday language as well as in mathematical contexts to denote a numeral or quantity, for example when stating that a number is five or when identifying a phone number. The term’s influence extends beyond Greek itself, shaping the historical and linguistic development of mathematical vocabulary in many languages through its cognates and through discussions of number theory and arithmetic.