merry, in strut and curry, in trap and marry, in lot and orange, in ago and sofa. Examples of long vowels: in fleece, in goose, in bear, in nurse and furry, in north, force and thought, in father and start. The long mid front vowel is elsewhere transcribed with the traditional symbol . The predominant realisation in contemporary RP is monophthongal. "Long" and "short" vowels Many conventional descriptions of the RP vowel system group the non-diphthongal vowels into the categories "long" and "short". This should not be taken to mean that English has minimal pairs in which the only difference is vowel length. "Long" and "short" are convenient cover terms for a number of phonetic features. The long-short pairings shown above include also differences in vowel quality. The vowels called "long" high vowels in RP and are slightly diphthongized, and are often narrowly transcribed in phonetic literature as diphthongs and . Vowels may be phonologically long or short (i.e. belong to the long or the short group of vowel phonemes) but their length is influenced by their context: in particular, they are shortened if a voiceless (fortis) consonant follows in the syllable, so that, for example, the vowel in 'bat' is shorter than the vowel in 'bad' . The process is known as pre-fortis clipping. Thus phonologically short vowels in one context can be phonetically longer than phonologically long vowels in another context. For example, the vowel called "long" in 'reach' (which ends with a voiceless consonant) may be shorter than the vowel called "short" in the word 'ridge' (which ends with a voiced consonant). Wiik, cited in , published durations of English vowels with a mean value of 17.2 csec. for short vowels before voiced consonants but a mean value of 16.5 csec for long vowels preceding voiceless consonants. In natural speech, the plosives and often have no audible release utterance-finally, and voiced consonants are partly or completely devoiced (as in ); thus the perceptual distinction between pairs of words such as 'bad' and 'bat', or 'seed' and 'seat' rests mostly on vowel length (though the presence or absence of glottal reinforcement provides an additional cue). Unstressed vowels are both shorter and more centralised than stressed ones. In unstressed syllables occurring before vowels and in final position, contrasts between long and short high vowels are neutralised and short and occur (e.g. happy , throughout ). The neutralisation is common