Phonology, as one of the central fields of linguistics, is the study of the system speakers use to represent and store linguistic information about the form of language items, other than their semantic or syntactic structures. This system converts units of sound in a spoken language or hand movements in a sign language[1] into abstract units of the mind, about which language users may have specific perceptions regarding their similarity, differences or how they pattern together. It is knowledge of a phonological system that allows an English speaker, for instance, to know without being told that fum could be an acceptable word but *fwe[2] could not, and it is the study of phonology that allows linguists to ask why and how that should be.
Although there are many ways of making a sound or moving a hand, phonologists are interested only in those which can be grouped into abstract linguistic units or categories. For example, they might examine how and why speakers of many languages perceive the difference between the sounds [l] and [r] to be nonsignificant,[3] whereas others consider them distinct enough to distinguish different words.[4] Phonology also goes beyond differences between individual sounds, involving topics such as syllable structure, stress, accent and intonation.
One task in phonology is to identify distinctive units within a language. For example, in English, the words pin and bin seem to each consist of three segments, with only the first differing. Phonologists may refer to these first units as different phonemes, and the contrast between /p/ and /b/ as phonemic - the two words are a minimal pair differing by only one phoneme. In pin and spin, on the other hand, though the two p sounds are phonetically rather different, English speakers would consider them the same /p/ phoneme. In other languages, for example Thai and Quechua, this same difference of aspiration[5] versus non-aspiration is phonemic, and therefore speakers will consider them to be significantly different. Though most phonologists no longer consider phonemes to be psychologically 'real', they remain in phonological study as a kind of shorthand for referring to more complex phonological representations that more adequately explain how such examples differ.[6]
Phonetics focuses on the physical sounds of speech, and thus it often informs phonological inquiry by showing how pronunciations are related.[7] However, since this sort of inquiry does not primarily concern itself with the study of abstract patterns in language, phoneticians' work usually complements linguistics, rather than constituting a central component.
Most writing systems, such as the Roman alphabet used for English, represent phonology in some way, such as the letter b indicating the phoneme /b/, though this relationship is often inexact. This relationship between reading and phonological knowledge is of concern to linguists interested in orthography (written language), language acquisition specialists, and educators concerned with developing literacy.[8]
Insert other topics here - e.g. intonation, stress
Native speakers of many languages may well have certain intuitions about how many 'beats' there are in a given word; for example, most English speakers would agree that there are two 'syllables' in the word butter but only one in but. That such phonological intuitions exist is one reason for phonologists to want to find about what syllables are; another reason is that assuming their existence explains a good deal about the way sounds and signs pattern in language.
Syllables cannot be defined through reference to breathing or articulatory movements; they are abstract, phonological units rather than a physical phenomenon. Syllables do not easily correspond to muscular contractions, for instance; nor do they correlate well with predictable changes in pitch.[9] Initially, defining syllables was such a difficult task that early generative phonology ignored it; only in the 1970s and 1980s was a serious reanalysis attempted.[10]
Since the syllable was reintroduced to phonological theory, it has come to be seen as essential in defining the behaviour of segments and stress in many languages. For instance, predicting whether a British English /l/ will be velarised or not is difficult without referring to positions within the syllable: if an [l] forms part of the rhyme of the syllable (the component containing the vowel or syllabic consonant) it will be velarised; if it is part of the onset (the initial part of the syllable), then it will not.[11] The syllable is one of the mechanisms that organise the order and positioning of segments.
Some explanation of the main theories, e.g. generative phonology, autosegmental phonology, phonology in optimality theory, government phonology, natural phonology