About Greek Numbers
(To be expanded.)
This page describes the ancient Greek alphabetic number system, in which the first nine letters of the alphabet represent 1-9, the next nine 10-90, and the last nine 100-900. (The older acrophonic system is more suited to books than webpages, since it cannot be represented in standard HTML characters.) Here is the complete chart:
Since there were only twenty-four symbols in actual use as letters, three archaic letters were taken out of retirement, as it were, to serve as numbers. These were digamma (ϝ = 6), qoppa (ϟ = 90), and sampi (ϡ = 900). For disambiguation, a tick like an uncurved apostrophe was put to the upper right of letters that were being used to indicate numbers, and a similar tick on the lower left instead of the upper right meant that the letters represented thousands, tens of thousands, or hundreds of thousands. A little practice with the Arabic → Greek Number Calculator should make things clear.
HTML is not ideal for Greek numbers. The official HTML qoppa looks very strange to me: a lightning-bolt or dog-leg rather than the usual lollipop. But these should do well enough.
The ancient Greeks and Romans had no clear concept of negative numbers, and therefore no symbol for them, so my calculators cannot handle them.