other reasons) only they are found in all of morpheme-initial, -internal, and -final positions, and native speakers typically perceive them as single units. Vowels English, much like other Germanic languages, has a particularly large number of vowel phonemes, and in addition the vowels of English differ considerably between dialects. Consequently, corresponding vowels may be transcribed with various symbols depending on the dialect under consideration. When considering English as a whole, lexical sets are often used, each named by a word containing the vowel or vowels in question. For example, the set consists of words which, like lot, have in Received Pronunciation and in General American. The " vowel" then refers to the vowel that appears in those words in whichever dialect is being considered, or (at a greater level of abstraction) to a diaphoneme, which represents this interdialectal correspondence. A commonly used system of lexical sets, devised by John C. Wells, is presented below; for each set, the corresponding phonemes are given for RP and General American, using the notation that will be used on this page. For a table that shows the pronunciations of these vowels in a wider range of English dialects, see IPA chart for English dialects. The following tables show the vowel phonemes of three standard varieties of English. The notation system used here for Received Pronunciation (RP) is fairly standard; the others less so. The feature descriptions given here (front, close, etc.) are abstracted somewhat; the actual pronunciations of these vowels are somewhat more accurately conveyed by the IPA symbols used (see Vowel for a chart indicating the meanings of these symbols; though note also the points listed below the following tables). The symbols given in the table are traditional but redirect to their modern implementation. The differences between these tables can be explained as follows: General American lacks a phoneme corresponding to RP (, ), instead using in the words and generally in the words. In a few North American accents, namely in Eastern New England (Boston), Western Pennsylvania (Pittsburgh), and to some degree in Pacific Northwest (Seattle, Portland) and Eastern Canadian English, words do not have the vowel of (the father–bother merger has not occurred) but instead merge with . Although the notation is used for the vowel of in RP and General American, the actual pronunciation is closer to a near-open central vowel in RP and advanced back in General American. The