Is the FLEECE vowel /iː/ a monophthong or a diphthong?

The vowel sound in FLEECE is phonemically transcribed as /iː/ in British English dictionaries /fliːs/.

However, when we pronounce it in different words, it is clearly not always long and not always monophthongal. In Standard Southern British English it becomes a little bit diphthongal before voiced consonants and in open endings.

Examples of the different lengths and possible transcriptions for the diphthongal qualities are below:

It’s also worth noting that the sound changes quite considerably in different accents throughout the UK and Ireland.

To learn more about these variations and for learning tips, see the new video lesson which you can watch here and includes a 10 question quiz.