TheAtticnumerals are asymbolic number notation used by theancient Greeks. They were also known asHerodianic numerals because they were first described in a 2nd-century manuscript byHerodian; or asacrophonic numerals (fromacrophony) because the basic symbols derive from the first letters of the(ancient) Greek words that the symbols represented.

The Attic numerals were a decimal (base 10) system, like the olderEgyptian and the laterEtruscan,Roman, andHindu-Arabic systems. Namely, the number to be represented was broken down into simple multiples (1 to 9) ofpowers of ten — units, tens, hundred, thousands, etc.. Then these parts were written down in sequence, in order of decreasing value. As in the basic Roman system, each part was written down using a combination of two symbols, representing one and five times that power of ten.

Attic numerals were adopted possibly starting in the 7th century BCE and although presently called Attic, they or variations thereof were universally used by the Greeks. No othernumeral system is known to have been used onAttic inscriptionsbefore the Common Era.^[1][2] Their replacement by theclassic Greek numerals started in other parts of the Greek World around the 3rd century BCE. They are believed to have served as model for the Etruscan number system, although the two were nearly contemporary and the symbols are not obviously related.^{[citation needed]}

The Attic numerals used the following main symbols, with the given values:^[1][2]

The symbols representing 50, 500, 5000, and 50000 were composites of an old form of the capital letterpi (with a short right leg) and a tiny version of the applicable power of ten. For example, 𐅆 was five times one thousand.

The fractions "one half" and "one quarter" were written "𐅁" and "𐅀", respectively.

The symbols were slightly modified when used to encode amounts intalents (with a small capitaltau, "Τ") or instaters (with a small capitalsigma, "Σ"). Specific numeral symbols were used to represent onedrachma ("𐅂") and tenminas "𐅗".

The use of "Η" (capitaleta) for 100 reflects the early date of this numbering system. In the Greek language of the time, the word for a hundred would be pronounced[hɛkaton] (with a "rough aspirated" sound /h/) and written "ΗΕΚΑΤΟΝ", because "Η" represented the sound /h/ in the Attic alphabet. In later, "classical" Greek, with the adoption of the Ionic alphabet throughout the majority of Greece, the letter eta had come to represent the long e sound while the rough aspiration was no longer marked.^[3][4] It was not untilAristophanes of Byzantium introduced the various accent markings during the Hellenistic period that thespiritus asper began to represent /h/, resulting in the spellingἑκατόν.^[5]

Multiples 1 to 9 of each power of ten were written by combining the two corresponding "1" and "5" digits, namely:

Unlike the more familiar Roman numeral system, the Attic system used only the so-called "additive" notation. Thus, the numbers 4 and 9 were writtenΙΙΙΙ andΠΙΙΙΙ, notΙΠ andΙΔ.

In general, the number to be represented was broken down into simple multiples (1 to 9) of powers of ten — units, tens, hundred, thousands, etc.. Then these parts would be written down in sequence, from largest to smallest value. For example:

• 49 = 40 + 9 = ΔΔΔΔ + ΠΙΙΙΙ =ΔΔΔΔΠΙΙΙΙ
• 2001 = 2000 + 1 = ΧΧ + I =ΧΧΙ
• 1982 = 1000 + 900 + 80 + 2 = Χ + 𐅅ΗΗΗΗ + 𐅄ΔΔΔ + ΙΙ =Χ𐅅ΗΗΗΗ𐅄ΔΔΔΙΙ
• 62708 = 60000 + 2000 + 700 + 8 = 𐅇Μ + ΧΧ + 𐅅ΗΗ + ΠΙΙΙ =𐅇ΜΧΧ𐅅ΗΗΠΙΙΙ.

• Etruscan numerals – Words, phrases and symbols for numbers of the Etruscan language
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• Greek numerals – System of writing numbers using Greek letters
• History of ancient numeral systems
• List of numeral system topics
• List of numeral systems

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