Greek script is used to write the Greek language (across its various historical phases), as well as Ottoman Turkish, Albanian, Karamanli Turkish, etc. Individual letters are also used as mathematical, linguistic and scientific symbols. The Greek script emerged from the Phoenician script, an abjad. Letterforms were first standardised around 402 BCE. The script was expanded during the Byzantine period: minuscule letterforms and new diacritics were introduced. Two orthographic standards exist: monotonic and polytonic. The polytonic system features diacritics for breathing variation and multiple tones, while the monotonic system limits itself to one tone mark. Monotonic Greek was devised in an orthographic reform in 1982. Polytonic Greek continues to be used in representations of older Greek-language texts, and in some special contexts for the modern Greek language itself.