The rough breathing comes from the left-hand half of the letter H. In some archaic Greek alphabets, the letter was used for , and this usage survives in the Latin letter H. In other dialects, it was used for the vowel , and this usage survives in the modern system of writing Ancient Greek, and in Modern Greek.
Usage
The rough breathing is placed over an initial vowel, or over the second vowel of an initial diphthong.
In some writing conventions, the rough breathing is written on the second of two rhos in the middle of a word. This is transliterated as rrh in Latin.
διάῤῥοια diárrhoia 'diarrhoea'
In crasis, when the second word has a rough breathing, the contracted vowel does not take a rough breathing. Instead, the consonant before the contracted vowel changes to the aspirated equivalent, if possible, and the contracted vowel takes the apostrophe or coronis.
τὸ ἕτερον → θοὔτερον 'the other one'
:tò héteron → thoúteron
Under the archaizinginfluence of Katharevousa, this change has been preserved in modern Greekneologisms coined on the basis of ancient words, e.g. πρωθυπουργός, from πρῶτος and ὑπουργός, where the latter was originally aspirated.
Technical notes
In Unicode, the code point assigned to the rough breathing is. It is intended to be used in all alphabetic scripts. It was also used in the original Latin transcription of Armenian for example with in t̔. The pair of space + combining rough breathing is. It may bind typographically with the letter encoded before it to its left, to create ligatures for example with in tʽ, and it is used for the modern Latin transcription of Armenian. It is also encoded for compatibility as mostly for usage in the Greek script, where it may be used before Greek capital letters to its right and aligned differently, e.g. with, where the generic space+combining dasia should be used after the letter it modifies to its left. Basically, U+1FFE was encoded for full roundtrip compatibility with legacy 8-bit encodings of the Greek script in documents where dasia was encoded before the Greek capital letter it modifies. When is used incorrectly after a Latin letter it is supposed to modify, for example with in t῾d, a visible small gap will occur between the leading Latin letter t and the Greek dasia, and the Greek dasia may interact typographically with the Latin letter d following it to suppress this gap, like in Greek. There is a polytonic Greek code range in Unicode, covering precomposite versions : Ἁ ἁ, Ἇ ἇ, ᾏ ᾇ, ᾉ ᾁ, Ἑ ἑ, Ἡ ἡ, Ἧ ἧ, ᾟ ᾗ, ᾙ ᾑ, Ἱ ἱ, Ἷ ἷ, Ὁ ὁ, Ῥ ῥ, Ὑ ὑ, Ὗ ὗ, Ὡ ὡ, Ὧ ὧ, ᾯ ᾧ, and ᾩ ᾡ. The rough breathing was also used in the early Cyrillic alphabet when writing the Old Church Slavonic language. In this context it is encoded as Unicode In Latin transcription of Semitic languages, especially Arabic and Hebrew, either or a symbol similar to it,, is used to represent the letter ayin. This left half ring may also be used for the Latin transcription of Armenian.