Attic Greek, like other dialects, was originally written in a local variant of the Greek alphabet. According to the classification of archaic Greek alphabets, which was introduced by Adolf Kirchhoff, the old-Attic system belongs to the "eastern" or "blue" type, as it uses the letters and with their classical values ( and ), unlike "western" or "red" alphabets, which used for and expressed with . In other respects, Old Attic shares many features with the neighbouring Euboean alphabet (which is "western" in Kirchhoff's classification). Like the latter, it used an L-shaped variant of lambda () and an S-shaped variant of sigma (). It lacked the consonant symbols xi () for and psi () for , expressing these sound combinations with and , respectively. Moreover, like most other mainland Greek dialects, Attic did not yet use omega () and eta () for the long vowels and . Instead, it expressed the vowel phonemes with the letter (which corresponds with classical , , ) and with the letter (which corresponds with , , and in later classical orthography). Moreover, the letter was used as heta, with the consonantal value of rather than the vocalic value of .