Diphthongs
BBC pronunciation has a large number of diphthongs - sounds which consist of a movement or
glide from one vowel to another. A vowel which remains constant and does not glide is called a
pure vowel.
In terms of length, diphthongs are similar to the long vowels described above. Perhaps the most
important thing to remember about all the diphthongs is that the first part is much longer and
stronger than the second part; for example, most of the diphthong (as in the words 'eye', 'I')
consists of the a vowel, and only in about the last quarter of the diphthong does the glide to I
become noticeable. As the glide to happens, the loudness of the sound decreases. As a result,
the part is shorter and quieter. Foreign learners should, therefore, always remember that the last
part of English diphthongs must not be made too strongly.
The total number of diphthongs is eight (though is increasingly rare). The easiest way to
remember them is in terms of three groups divided as in this diagram