Wikipedia
Broad On (Ѻ ѻ; italics: Ѻ ѻ) is a positional and orthographical variant of the Cyrillic letter O (О о) (here "on" (, onŭ) is a traditional name of Cyrillic letter О; these names are still in use in the Church Slavonic alphabet).
Broad On is used only in the Church Slavonic language. In its alphabet (in primers and grammar books), broad and regular shapes of О/о share the same position. Uppercase is typically represented by broad Ѻ, and lowercase is either regular о or dual: both broad ѻ and regular о (in the same way as Greek uppercase Σ is accompanied with two lowercases σ, ς). Phonetically, broad Ѻ/ѻ is the same as regular О/о.
In standard Church Slavonic orthography (since the middle of the 17th century until present time), the broad shape of letter On is used instead of the regular shape of the same letter in the following cases:
- as the first letter of a word's root:
- in the initial position (ѻгнь, ѻтрокъ),
- after a prefix (праѻтецъ),
- in compound words (ѻбоюдуѻстрый),
- in two geographical names (іѻрданъ— Jordan River, іѻппіа—city of Jaffa) and their derivatives,
- as the numerical sign to represent the number 70.
(However, Church Slavonic editions printed outside Russian Empire have often ignored the last rule and used regular о as the numerical sign).
Historically, Broad On was also used in the later Old Russian period, including documents, letters and other vernacular texts, to signal the initial position of a word or a syllable or occasionally to mark a closed vowel (developed in North Russian dialects since the XIV century). It is found in birch bark manuscripts and in some other Russian texts. Other glyphs could be used in the same functions, including Monocular O and Cyrillic Omega.
Usage examples of "broad on".
Chamberlain had been sailing east on a reach, with the wind broad on the starboard quarter.
He turned to the windows and saw the good sunlight lying broad on green vines and brown river and the white sails of ships.
The rock bridge was broad on which they crossed, but even so it was past midnight before the host was camped in the plain beyond.
He stopped to stretch and yawn, and only then took notice that the Big Dipper and the North Star hung broad on the port beam, and that the yellow moon was sinking dead astern.