English phonology refers to the system of speech sounds that are used in spoken English. Like many other languages, English has wide variation in pronunciation, both historically and from dialect to dialect. In general, however, the regional dialects of English share a largely similar (but not identical) phonological system. Among other things, most dialects have vowel reduction in unstressed syllables and a complex set of phonological features that distinguish fortis and lenis consonants (stops, affricates, and fricatives). Phonological analysis of English often concentrates on or uses, as a reference point, one or more of the prestige or standard accents, such as Received Pronunciation for England, General American for the United States, and General Australian for Australia. Nevertheless, many other dialects of English are spoken, which have developed independently from these standardized accents, particularly regional dialects. Information about these standardized accents functions only as a limited guide to all of English phonology, which one can later expand upon once one becomes more familiar with some of the many other dialects of English that are spoken. Phonemes A phoneme of a language or dialect is an abstraction of a speech sound or of a group of different sounds which are all perceived to have the same function by speakers of that particular language or dialect. For example, the English word through consists of three phonemes: the initial "th" sound, the "r" sound, and a vowel sound. The phonemes in this and many other English words do not always correspond directly to the letters used to spell them (English orthography is not as strongly phonemic as that of many other languages). The number and distribution of phonemes in English vary from dialect to dialect, and also depend on the interpretation of the individual researcher. The number of consonant phonemes is generally put at 24 (or slightly more depending on the dialect). The number of vowels is subject to greater variation; in the system presented on this page there are 20–25 vowel phonemes in Received Pronunciation, 14–16 in General American and 19–21 in Australian English. The pronunciation keys used in dictionaries generally contain a slightly greater number of symbols than this, to take account of certain sounds used in foreign words and certain noticeable distinctions that may not be—strictly speaking—phonemic. Consonants The following table shows the 24 consonant phonemes found in most dialects of English, plus , whose distribution is more limited. Fortis consonants