Greek numerals are a system of representing numbers using letters of the Greek alphabet. They are also known by the names Ionian numerals, Milesian numerals (from Miletus in Ionia), Alexandrian numerals, or alphabetic numerals (in common with other alphabetic numerations). In modern Greece, they are still used for ordinal numbers and in situations similar to those in which Roman numerals are still used elsewhere in the West. For ordinary cardinal numbers numbers, however, Greece uses Arabic numerals.
Originally, before the adoption of the Greek alphabet, Linear A and Linear B had used a different system, called Aegean numbers, with symbols for 1, 10, 100, 1000 and 10000 operating with the following formula: | = 1, – = 10, ◦ = 100, ¤ = 1000, ☼ = 10000.
The earliest alphabet-related system of numerals used with the Greek letters was a set of the acrophonic Attic numerals, operating much like Roman numerals (which derived from this scheme), with: Ι = 1, Π = 5, Δ = 10, Η = 100, Χ = 1000, Μ = 10000; and with 50, 500, 5000, and 50000 represented by composites of Π and a tiny version of the applicable power of ten. The acrophonic system was replaced by a new alphabetic system, sometimes called the Ionic numeral system, from the 4th century BCE.