Editing Received Pronunciation (section)

===="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 RP has [[minimal pair]]s 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 vowel]]s in RP {{IPA|/iː/}} and {{IPA|/uː/}} are slightly [[diphthong]]ized, and are often narrowly transcribed in phonetic literature as diphthongs {{IPA|[ɪi]}} and {{IPA|[ʊu]}}.{{sfnp|Roach|2009|p=20}}{{efn|{{harvtxt|Roach|2009|p=20}}'s notes on one of the reasons for not treating these two phonemes as diphthongs: "I mention above that {{IPA|iː}}, {{IPA|uː}} are often pronounced as slightly diphthongal: although this glide is often noticeable, I have never found it helpful to try to teach foreign learners to pronounce {{IPA|iː}}, {{IPA|uː}} in this way."}} The starting point of the diphthongal {{IPA|/uː/}} can be either close to {{IPA|[ʊ]}} or a more centralised and even unrounded {{IPA|[ɨ̞]}}, and its narrow transcriptions could be either {{IPA|[ʊu]}} or {{IPA|[ɨ̞ɯ̈]}}.{{sfnp|Cruttenden|2014|p=133}}

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|fortis]]) consonant follows in the syllable, so that, for example, the vowel in ''bat'' {{IPA|[bæʔt]}} is shorter than the vowel in ''bad'' {{IPA|[bæˑd]}}. The process is known as [[Clipping (phonetics)|''pre-fortis clipping'']]. Thus phonologically short vowels in one context can be phonetically ''longer'' than phonologically long vowels in another context.{{sfnp|Roach|2004|p=241}} For example, the vowel called "long" {{IPA|/iː/}} in ''reach'' {{IPA|/riːtʃ/}} (which ends with a voiceless consonant) may be shorter than the vowel called "short" {{IPA|/ɪ/}} in the word ''ridge'' {{IPA|/rɪdʒ/}} (which ends with a voiced consonant). Wiik,{{sfnp|Wiik|1965}} cited in {{harvcol|Cruttenden|2014}}, published durations of English vowels with a mean value of 172 [[Millisecond|ms]] for short vowels before voiced consonants but a mean value of 165&nbsp;ms for long vowels preceding voiceless consonants.{{sfnp|Cruttenden|2014|p=101}}

In [[natural speech]], the plosives {{IPA|/t/}} and {{IPA|/d/}} often have no audible release utterance-finally, and voiced consonants are partly or completely devoiced (as in {{IPA|[b̥æˑd̥]}}); 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).{{sfnp|Cruttenden|2014|p=}}

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 {{IPA|[i]}} and {{IPA|[u]}} occur (e.g. ''happy'' {{IPA|[ˈhæpi]}}, ''throughout'' {{IPA|[θɹuˈaʊʔt]}}).{{sfnp|Roach|2004|pp=241, 243}} The neutralisation is common throughout many English dialects, though the phonetic realisation of e.g. {{IPA|[i]}} rather than {{IPA|[ɪ]}} (a phenomenon called [[happy-tensing|''happy''-tensing]]) is not as universal.

According to phonetician [[Jane Setter]], the typical pronunciation of the short variant of {{IPA|/uː/}} is a weakly rounded [[near-close near-back rounded vowel]] {{IPAblink|ʊ|ʊ̜}}.<ref>{{cite web |title=A World of Englishes: Is {{IPA|/ə/ |cat=no}} "real"? |date=19 June 2013 |url=http://aworldofenglishes.blogspot.com/2013/06/is-real.html |access-date=5 March 2016}}</ref>