The International Phonetic Alphabet (IPA)

First published in 1888, and revised several times since (most recently in 2005) in the light of new discoveries, the International Phonetic Alphabet provides a notational standard for the phonetic representation of all languages. The IPA uses symbols representing speech sounds, which are conventionally placed in square brackets. Unlike conventional written characters or graphemes, IPA symbols have a constant value, so while the letter g is pronounced differently in gap, gnaw and beige, the symbol [g] always represents a voiced velar plosive, i.e. the sound in gap.

The founders of the International Phonetic Association were French and British linguists, so it is not surprising that IPA symbols are heavily influenced by those languages. Many of the symbols are taken from Latin script and the cardinal vowels chosen as anchor points correspond fairly well to those of standard French. Other symbols have been drawn from other writing systems, for example [θ] (the first consonant in think) is taken from Greek, while its voiced equivalent [ð] (as in this) is the letter eth from Icelandic. Diacritics on symbols provide further precision where required: , for example, indicates a vowel more open than [o] but closer than  ; a straight diacritic below a consonant indicates that it is syllabic, as for example for the second syllable in listen .

As the phonetics of less familiar languages have become better known, entirely new symbols have had to be created. Some Southern African languages, for example, have clicks produced by a sucking action in the mouth. A dental click ) represents the tut, tut! sound used in English to convey disapproval, while the lateral click  is the sound often used by English speakers to get a horse to move. The symbol for a bilabial click  reflects the lip-closure akin to kissing with which this sound is produced.