Correspondence With Pronunciation
Orthographies that use alphabets and syllabaries are based on the principle that the written symbols (graphemes) correspond to units of sound of the spoken language: phonemes in the former case, and syllables in the latter. However, in virtually all cases, this correspondence is not exact. Different languages' orthographies offer different degrees of correspondence between spelling and pronunciation. English orthography, for example, is highly irregular, whereas the orthographies of languages such as Russian, Spanish and Finnish represent pronunciation much more faithfully, although the correspondence between letters and phonemes is still not exact.
An orthography in which the correspondences between spelling and pronunciation are highly complex or inconsistent is called a deep orthography (or less formally, the language is said to have irregular spelling). An orthography with relatively simple and consistent correspondences is called shallow (and the language has regular spelling).
One of the main reasons for which spelling and pronunciation deviate is that sound changes taking place in the spoken language are not always reflected in the orthography, and hence spellings correspond to historical rather than present-day pronunciation. One consequence of this is that many spellings come to reflect a word's morphophonemic structure rather than its purely phonemic structure (for example, the English regular past tense morpheme is consistently spelled -ed in spite of its different pronunciations in various words). This is discussed further at Phonemic orthography: Morphophonemic features.
The syllabary systems of Japanese (hiragana and katakana) are examples of almost perfectly shallow orthographies – the kana correspond with almost perfect consistency to the spoken syllables, although with a few exceptions where symbols reflect historical or morphophonemic features: notably the use of ぢ ji and づ zu (rather than じ ji and ず zu, their pronunciation in standard Tokyo dialect) when the character is a voicing of an underlying ち or つ (see rendaku), and the use of は, を, and へ to represent the sounds わ, お, and え, as relics of historical kana usage.
The Korean hangul system was also originally an extremely shallow orthography, but as a representation of the modern language it frequently also reflects morphophonemic features.
For full discussion of degrees of correspondence between spelling and pronunciation in alphabetic orthographies, including reasons why such correspondence may break down, see Phonemic orthography.
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