Archaic and Classical Greek vowels and diphthongs varied by dialect. The tables below show the vowels of Classical Attic in the IPA, paired with the vowel letters that represent them in the standard Ionic alphabet. The earlier Old Attic alphabet had certain differences. Attic Greek of the 5th century BC likely had 5 short and 7 long vowels: and . Vowel length was phonemic: some words are distinguished from each other by vowel length. In addition, Classical Attic had many diphthongs, all ending in or ; these are discussed below.