From The Art and Popular Culture Encyclopedia
Phonology (from the φωνή, phōnē, "voice, sound" and λόγος, lógos, "word, speech, subject of discussion") is the systematic use of sound to encode meaning in any spoken human language, or the field of linguistics studying this use. Just as a language has syntax and vocabulary, it also has a phonology in the sense of a sound system. When describing the formal area of study, the term typically describes linguistic analysis either beneath the word (e.g., syllable, onset and rime, phoneme, articulatory gesture, articulatory feature, mora, etc.) or to units at all levels of language that are thought to structure sound for conveying linguistic meaning. It is viewed as the subfield of linguistics that deals with the sound systems of languages. Whereas phonetics is about the physical production, acoustic transmission and perception of the sounds of speech, phonology describes the way sounds function within a given language or across languages to encode meaning. The term 'phonology' has been used in the linguistics of the 20th century as a cover term uniting phonemics and phonetics. Current phonology can interface with disciplines such as psycholinguistics and speech perception, resulting in specific areas like articulatory or laboratory phonology.
An important part of traditional forms of phonology have been studying which sounds can be grouped into distinctive units within a language. For example, the [p] sound in "pot" is described as including the articulatory feature of aspirated, while the word- and syllable-final [p] in "soup" is not aspirated (indeed, it might be realized as a glottal stop). However, English speakers intuitively treat both sounds as variations of the same phonological category; that is, the English phoneme /p/. Traditionally, it might typically be argued that if a word-initial, aspirated [p] were interchanged with the word-final, unaspirated [p] in "soup", they would still perceive the 'same' /p/ (though speech perception findings now put this theory in doubt). Still, some sort of 'sameness' holds in English but not universally in all other languages. For example, in Thai and Quechua, this difference of aspiration or non-aspiration differentiates phonemes and coincides with lexical contrasts dependent on minimal differences. In addition to the minimal meaningful sounds (the phonemes), phonology studies how sounds alternate, such as the /p/ in English, and topics such as syllable structure, stress, accent, and intonation.
The principles of phonological theory have also been applied to the analysis of sign languages, even though the sub-lexical units are not instantiated as speech sounds. The principles of phonological analysis can be applied independently of modality because they are designed to serve as general analytical tools, not language-specific ones. On the other hand, it must be noted, it is difficult to analyze phonologically a language one does not speak, and most phonological analysis takes place with recourse to phonetic information.