not precede a vowel), many of the vowels can be r-colored by way of realization of a following . This is often transcribed phonetically using a vowel symbol with an added retroflexion diacritic ; thus the symbol has been created for an r-colored schwa (sometimes called schwar) as in , and the vowel of can be modified to make so that the word start may be transcribed . Alternatively, the sequence might be written to indicate an r-colored offglide. The vowel of is generally always r-colored in these dialects, and this can be written (or as a syllabic ). In modern RP and other dialects, many words from the group are coming to be pronounced by an increasing number of speakers with the vowel (so sure is often pronounced like shore). The vowels of and are commonly pronounced as narrow diphthongs, approaching and , in RP. Near-RP speakers may have particularly marked diphthongization of the type and , respectively. In General American, the pronunciation varies between a monophthong and a diphthong. Allophones of vowels Listed here are some of the significant cases of allophony of vowels found within standard English dialects. Vowels are shortened when followed in a syllable by a voiceless (fortis) consonant. This is known as pre-fortis clipping. Thus in the following word pairs the first item has a shortened vowel while the second has a normal length vowel: 'right' – 'ride' ; 'face' – 'phase' ; 'advice' – 'advise' . In many accents of English, tense vowels undergo breaking before , resulting in pronunciations like for peel, for pool, for pail, and for pole. In RP, the vowel may be pronounced more back, as , before syllable-final , as in goal. In standard Australian English the vowel is similarly backed to before . A similar phenomenon may occur in Southern American English. The vowel is often pronounced in open syllables. The and diphthongs may be pronounced with a less open starting point when followed by a voiceless consonant; this is chiefly a feature of Canadian speech (Canadian raising), but is also found in parts of the United States. Thus writer may be distinguished from rider even when flapping causes the and to be pronounced identically. Unstressed syllables Unstressed syllables in English may contain almost any vowel, but in practice vowels in stressed and unstressed syllables tend to use different inventories of phonemes. In particular, long vowels are