arithmós

Arithmós (Greek ἄριθμος) is the Greek noun for "number" or "numeral." In classical Greek, arithmós denoted the abstract concept of a number used in counting as well as the symbols employed to represent that concept. The term underpins the modern word arithmetic, as well as related mathematical vocabulary in Greek and other languages.

In ancient Greek mathematics, arithmós referred to natural numbers and to the branch of mathematics dealing with counting and calculation, later known as arithmetic. Pythagoreans and other Greek scholars treated arithmoi as foundational objects or quantities, distinct from geometric magnitudes. The Greek numeral system—using letters to encode numbers—made arithmoi central to computational practice and demonstrations.

In modern Greek, arithmós continues to mean "number," with arithmetiki meaning arithmetic. The term's influence extends to many languages: the English word "arithmetic" derives from Latin arithmetica, ultimately from Greek arithmētiki.

In scholarly usage, arithmós is often encountered in historical discussions of numbers and number theory in ancient Greek sources.