Greek alphabet glottal ("heth") was borrowed in two different functions by different dialects of Greek: as a letter for /h/ (Η, heta) by those dialects that had such a sound, and as an additional vowel letter for the long (Η, eta) by those dialects that lacked the consonant. Eventually, a seventh vowel letter for the long (Ω, omega) was introduced. Greek also introduced three new consonant letters for its aspirated plosive sounds and consonant clusters: Φ ("phi") for , Χ ("chi") for and Ψ ("psi") for . In western Greek variants, Χ was instead used for and Ψ for . The origin
History of the Greek alphabet of the Stoudion monastery in Constantinople. The earliest type of books written in minuscule, dated from the mid-9th to mid-10th century, are called codices vetustissimi ('oldest codices'). During the following centuries, this style of writing was further developed and took on more cursive elements again. This became the dominant type of handwriting until the post-Byzantine period. Together with the minuscule letter shapes, Greek writing also began to use word-boundary spaces and diacritics (i.e. the accent marks and breathings of polytonic orthography) more regularly. Some punctuation began also to be employed. The iota subscript was employed from the 13th century onwards.