Local accents are part of local dialects. Any dialect of English has unique features in pronunciation, vocabulary, and grammar. The term “accent” describes only the first of these, namely, pronunciation. Non-native speakers of English tend to carry over the intonation and phonemic inventory from their mother tongue into their English speech.
Among native English speakers, many different accents exist. Some regional accents, such as Pennsylvania Dutch English, are easily identified by certain characteristics. Further variations are to be found within regions, for example, towns located less than 10 miles (16 km) from the City of Manchester such as Bolton, Oldham and Salford, each have distinct accents, all of which form the Lancashire accent, yet in extreme cases are different enough to be noticed even by a non-local listener.
There is also much room for misunderstanding between people from different regions, as the way one word is pronounced in one accent (for example, petal in American English) will sound like a different word in another accent (for example, pearl in Scottish English).
Dialects can be usefully defined as sub-forms of languages which are, in general, mutually comprehensible;. British linguists distinguish dialect from accent, which refers only to pronunciation. Thus, any educated English speaker can use the vocabulary and grammar of Standard English, but different speakers use their own local words for everyday objects or actions, regional accent, or Received Pronunciation, which within the U.K. is considered an accent distinguished by class rather than by region. American linguists, however, include pronunciation differences as part of the definition of regional or social dialects.
The combination of differences in pronunciation and use of local words may make some English dialects almost unintelligible to speakers from other regions. The major native dialects of English are often divided by linguists into the three general categories of the British Isles dialects, those of North America, those of Australasia, and those of South Africa.
The dialect of British English which is presented in dictionaries is usually known as Received Pronunciation (English as spoken by the upper class and the Queen, for example), or simply RP. Like other accents, RP is subject to variation and change: