Such imperfections are nothing new. The Greek alphabet has been defective for its entire history. 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, the names of five letters were pronounced with initial vowels by the Greeks and used to represent vowels. These were alpha , e (later called e psilon), iota , o (later called o micron, and u (later called u psilon): 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, 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.

A famously defective alphabet is the Arabic one. The modern script does not generally write short vowels, but for the first few centuries of the Islamic era, many consonant letters were ambiguous as well. The Arabic alphabet derives from the Aramaic, and not only did the Aramaic language have fewer phonemes than Arabic, but several originally distinct Aramaic letters had conflated (become indistinguishable in shape), so that in the early Arabic writings 18 letters had to do duty for 28 consonant phonemes — and in the middle of words, only 15 were distinct. For example, medial <ﯩ> represented /b, t, θ, n, j/, and <ﺡ>, /g, ħ, x/. A system of diacritic marks, or pointing, was later developed to resolve the ambiguities, and over the centuries became nearly universal. However, even today unpointed texts of a style called mašq are found.

Without short vowels or geminate consonants being written, Arabic نظر nẓr could represent /nażara/ 'he saw', /naẓẓara/ 'he compared', /nuẓira/ 'he was seen', /nuẓẓira/ 'he was compared', /naẓar/ 'a glance', or /niẓr/ 'similar'. However, in practice there is little ambiguity, as the vowels are more easily predictable in Arabic than they are in a language like English. Moreover, the defective nature of the script has its benefits: the stable shape of the root words, despite grammatical inflection, results in quicker word recognition and therefore faster reading speeds;^{[citation needed]} and the lack of short vowels, the sounds which vary the most between Arabic dialects, makes texts more widely accessible to a diverse audience.

However, in mašq and those styles of kufic writing which lack consonant pointing, the ambiguities are more serious, for here different roots are written the same. ﯨطر could represent the root nẓr 'see' as above, but also nţr 'protect', bţr 'pride', bẓr 'clitoris' or 'with flint', as well as several inflections and derivations of each of these root words.

• Defective verb