Digamma

Whereas it was originally called waw or wau, its most common appellation in classical Greek is digamma; as a numeral, it was called episēmon during the Byzantine era and is now known as stigma after the Byzantine ligature combining σ-τ as ϛ. Digamma or wau was part of the original archaic Greek alphabet as initially adopted from Phoenician.

Like its model, Phoenician waw, it represented the voiced labial-velar approximant /w/ and stood in the 6th position in the alphabet between epsilon and zeta.

In Ionic, /w/ had probably disappeared before Homer's epics were written down (7th century BC), but its former presence can be detected in many cases because its omission left the meter defective.

Further evidence coupled with cognate-analysis shows that οἶνος was earlier ϝοῖνος /wóînos/[3] (compare Cretan Doric ibêna and Latin vīnum, which is the origin of English wine[4]).

In some local (epichoric) alphabets, a variant glyph of the letter digamma existed that resembled modern Cyrillic И.

[5] Digamma/wau remained in use in the system of Greek numerals attributed to Miletus, where it stood for the number 6, reflecting its original place in the sequence of the alphabet.

During their history in handwriting in late antiquity and the Byzantine era, all three of these symbols underwent several changes in shape, with digamma ultimately taking the form of "ϛ".

The shape , during the archaic period, underwent a development parallel to that of epsilon (which changed from to "E", with the arms becoming orthogonal and the lower end of the stem being shed off).

It then developed a downward tail at the end (, ) and finally adopted a shape like a Latin "s" ()[8] These cursive forms are also found in stone inscriptions in late antiquity.

[7] In the ninth and tenth centuries, the cursive shape digamma was visually conflated with a ligature of sigma (in its historical "lunate" form) and tau ( + = , ).

Several different shapes of uppercase stigma can be found, with the lower end either styled as a small curved S-like hook (), or as a straight stem, the latter either with a serif () or without one ().

It has a modern lowercase form (ϝ) that typically differs from Latin "f" by having two parallel horizontal strokes like the uppercase character, with the vertical stem often being somewhat slanted to the right or curved, and usually descending below the baseline.

Wau (variously rendered as vau, waw or similarly in English) is the original name of the alphabetic letter for /w/ in ancient Greek.

This form itself is not historically attested in Greek inscriptions, but the existence of the name can be inferred from descriptions by contemporary Latin grammarians, who render it as vau.

[16] It is also found in a number of western European accounts of the Greek alphabet written in Latin during the early Middle Ages.

One of them is the work De loquela per gestum digitorum, a didactic text about arithmetics attributed to the Venerable Bede, where the three Greek numerals for 6, 90 and 900 are called "episimon", "cophe" and "enneacosis" respectively.

From Scaliger, the term found its way into modern academic usage in this new meaning, of referring to complementary numeral symbols standing outside the alphabetic sequence proper, in Greek and other similar scripts.

[19] In one remark in the context of a biblical commentary, the 4th century scholar Ammonius of Alexandria is reported to have mentioned that the numeral symbol for 6 was called gabex by his contemporaries.