Defective script

A defective script is a script that does not represent all the phonemic distinctions of a language.

For example, Classical Greek had distinctive vowel length: 5 short vowels, /i e a o u/, and 7 long vowels, /iː eː ɛː aː ɔː oː uː/. When the Phoenician alphabet was adapted to Greek, five letters had vowel-initial names and were used to represent vowels. These were alpha, e (later called epsilon), iota, o (later called omicron, and u (later called upsilon): five letters for twelve vowel sounds. Later the [h] dropped from the Eastern Greek dialects, and the letter heta (now pronounced eta) became available; it was used for /ɛː/. About the same time the Greeks created an additional letter, omega, probably by writing omicron with an underline, and that was used for /ɔː/. Digraphs ei and ou were devised for /eː oː/. Thus Greek entered its classical era with seven letters and two digraphs for twelve vowel sounds. Long /iː aː uː/ were never distinguished from short /i a u/, even though the distinction was meaningful. Although the Greek alphabet was a good match to the consonants of the language, it was defective when it came to the vowels.