S(IV). SUMMARY OF PHONOLOGYPhonology is the systematic study of the sounds used in language, their internal structure, and their composition into syllables, words and phrases. Computational phonology is the application of formal and computational techniques to the representation and processing of phonological information. This chapter will present the fundamentals of descriptive phonology along with a brief overview of computational phonology. 1.1 Phonological contrast, the phoneme, and distinctive features There is no limit to the number of distinct sounds that can be produced by the human vocal apparatus. However, this infinite variety is harnessed by human languages into sound systems consisting of a few dozen language-specific categories, or phonemes. An example of an English phoneme is t. English has a variety of t-like sounds, such as the aspirated t h of ten the unreleased t of net, and the flapped R of water (in some dialects). In English, these distinctions are not used to differentiate words, and so we do not find pairs of English words which are identical but for their use of t h versus t. (By comparison, in some other languages, such as Icelandic and Bengali, aspiration is contrastive.) Nevertheless, since these sounds (or phones, or segments) are phonetically similar, and since they occur in complementary distribution (i.e. disjoint contexts) and cannot differentiate words in English, they are all said to be allophones of the English phoneme t. Of course, setting up a few allophonic variants for each of a finite set of phonemes does not account for the infinite variety of sounds mentioned above. If one were to record multiple instances of the same utterance by the single speaker, many small variations could be observed in loudness, pitch, rate, vowel quality, and so on.