2345: Digamma: Greek's Ghost Letter May 20, 2021

The letter G effectively replaced the letter Z in the Latin alphabet, but in the Greek alphabet the letter Ζ,ζ was also affected in its order in the alphabeta. The Hebrew and Phoenician letters, zayin, are both 7th and as numerals means (7) as is true in Greek numerals despite it being 6th in order. This is because the letter Ϛ,Ϝ known as Digamma which used to be 6th was used and eventually disfavored, merging with Sigma—namely the Lunate Sigma—creating the only Greek letter with 3 distinct forms (capital, lower case, and word-final). This had originally represented the sound /w/ which no longer exists in Greek.

2224: Lunate Sigma Jan 16, 2021

The Greek letter sigma is special in its design in a number of ways. It is the only to have 3 forms: Σ, σ, and ς (the last only found at the end of words), but even these are not the only way it's looked. The Lunate Sigma used in Greek of the Hellenistic period, was written in a C-like shape, now known as the Lunate Sigma (uppercase Ϲ, lowercase ϲ) called as such in reference to the Moon. This should not be confused for the Latin letter C/c. It only has two forms, laking the distinct word-final form that is found today. These days, it is mostly found in religious contexts or other decorative fonts.