| Decimal | Symbol | Greek numeral |
|---|---|---|
| 1 | Ι | ἴος (ios) |
| 5 | Π | πέντε (pente) |
| 10 | Δ | δέκα (deka) |
| 100 | Η | hεκατόν (hekaton) |
| 1000 | Χ | χίλιοι (khilioi) |
| 10000 | Μ | μύριοι (myrioi) |
The use of Ι for 1 has been hypothesised to be motivated by the word form ἴος, attested as an archaic variant of εἵς 'one' in Homer. The use of Η for 100 reflects the early date of this numbering system: Η (Eta) in the early Attic alphabet represented the sound /h/. 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. It wasn't until Aristophanes of Byzantium introduced the various accent markings during the Hellenistic period that the spiritus asper began to represent /h/. Thus the word for a hundred would originally have been written ΗEΚΑΤΟΝ, as compared to the now more familiar spelling ἑκατόν. In modern Greek, the /h/ phoneme has disappeared altogether, but this has had no effect on the basic spelling.
Unlike the more familiar Modern Roman numeral system, the Attic system contains only additive forms. Thus, the number 4 is written ΙΙΙΙ, not ΙΠ.
The numerals representing 50, 500, and 5,000 were composites of pi (often in an old form, with a short right leg) and a tiny version of the applicable power of ten. Thus, delta under pi combined into one symbol represented 50, eta under pi represented 500 and khi under pi represented 5000.
| I | | | | Δ | | Δ | | Η | | Η | | X | | X | | M |
|---|---|---|---|---|---|---|---|---|
| 1 | 5 | 10 | 5 × 10 | 100 | 5 × 100 | 1000 | 5 × 1000 | 10000 |
| 50 | 500 | 1000 × 5 | 1000 × 10 | |||||
| I | V | X | L | C | D | M | V | X |