The Greeks used two number systems, one mainly for currency and everyday counting and a more sophisticated number system which was used by the learned. Strictly speaking there were many Greek number systems, since each island had their own system however they were all pretty similar.
The everyday acrophonic system was similar to the Egyptian. A ‘rod’ or the letter I was used to count units, i.e. the numbers 1 to 4. A new symbol was introduced for 5. The Greeks took the first letter of the word five to symbolise that. The word five in Greek is Pente (think ‘pentagon’), so the letter used was ‘Pi’ the Greek ‘P’: \(\Pi\), The word ten in Greek is Dekka (think ‘decagon’), so the letter used was ‘Delta’ the Greek ‘D’: \(\Delta\), and so on (in the quiz later on, you will be challenged to decipher other Greek numerals…).
The intellectual elite used many more symbols for their numbers, mainly for ‘scientific’ writing. In fact, they used all the letters of the alphabet, and in multiple ‘case’ or ‘font’. They probably did this to reduce the length of the numbers they wrote, however this made number reading difficult. Here is a glance of their system: For the numbers 1-9, they used:
Then, we have the ‘tens’:
and the ‘hundreds’:
Numbers were constructed using addition, for example, the number 429 would be written: \(\upsilon\kappa\theta\). Numbers larger than 999 were constructed using extra symbols denoting the thousands ten thousands etc. in a similar way that a ‘bar’ was written over large Roman numerals for the same purpose. To denote thousands a subscript or superscript iota, \(\iota\) was used. \(_\iota\epsilon\upsilon\kappa\theta\) would be 5429.
The fact that all the numbers can be represented by letters, the art of Isopsephy, giving words a numeric value and vice-versa, arose. This is similar to the Hebrew Gematria which was widely practiced throughout the ages. The Greek word fire: \(\pi\upsilon\rho\), for example has a numeric value of \(\pi+\upsilon+\rho=80+400+100=580\).
If all of this interests you, you may want to learn ancient Greek! Here is a great site to start, but don’t forget to return to the course. We still have a lot of things to learn…
Join the discussion and share some other numeral systems with us.
© Davidson Institute of Science Education, the educational arm of the Weizmann Institute of Science