Unlike Greek, the Slavic languages had only a single /ɔ/ sound, so Omega was little used compared to the letter O (О о), descended from the Greek letter Omicron.

In the older ustav writing, Omega was used mainly for its numeric value of 800, and rarely appeared even in Greek words.

Modern Church Slavonic has developed strict rules for the use of these letterforms.

It descends from the Greek omega with the smooth breathing (psili) and circumflex (perispomeni) diacritical marks (Ὦ ὦ), also used in the corresponding exclamation in ancient Greek.

This article related to the Cyrillic script is a stub.