symbol continues to be used for reasons of tradition (it was historically a back vowel) and because it is still back in other varieties. RP transcriptions use rather than largely for convenience and historical tradition; it does not necessarily represent a different sound from the General American phoneme, although the RP vowel may be described as somewhat less open than the American one. The different notations used for the vowel of in RP and General American ( and ) reflect a difference in the most common phonetic realizations of that vowel. The triphthongs given in the RP table are usually regarded as sequences of two phonemes (a diphthong plus ); however, in RP, these sequences frequently undergo smoothing into single diphthongs or even monophthongs. The different notations used here for some of the Australian vowels reflect the phonetic realization of those vowels in Australian: a central rather than in , a more closed rather than in , a close-mid rather than traditional RP's in , an open-mid rather than traditional RP's in , an opener rather than somewhat closer in , a central rather a back in and , and somewhat different pronunciations of most of the diphthongs. Note that central in , close-mid in and open-mid in are standard realizations in modern RP and the difference between modern RP and Australian English in these vowels lies almost only in transcription rather than pronunciation. Both Australian and RP are long monophthongs, the difference between them being in tongue height: Australian is close-mid , whereas the corresponding RP vowel is open-mid . Other points to be noted are these: The vowel is coming to be pronounced more open (approaching ) by many modern RP speakers. In American speech, however, there is a tendency for it to become more closed, tenser and even diphthongized (to something like ), particularly in certain environments, such as before a nasal consonant. Some American accents, for example those of New York City, Philadelphia and Baltimore, make a marginal phonemic distinction between and , although the two occur largely in mutually exclusive environments. See :/æ/ raising. A significant number of words (the group) have in General American, but in RP. The pronunciation varies between and in Australia, with speakers from South Australia using more extensively than speakers from other regions. In General American and Canadian (which are rhotic accents, where is pronounced in positions where it does