To transcribe a diphthong, we need two symbols: the first indicating the starting position and the second indicating the finishing position or the direction of movement.
In the English diphthong [aj], the tongue body starts in the position
for [a] -- between [æ] and [
]. Almost immediately, it begins moving upwards
and forwards. Occasionally it gets as far as [i], but usually only as
far as [
] or even
lower. In a broader transcription, we can ignore the exact position of
the end-point and simply use the glide [j] as a cover symbol.
In the English diphthong [aw], the tongue body starts out in the same
position (for most Canadian speakers) and moves upwards and backwards,
towards [u], [
], or
[o]. In a broader transcription, we can use the glide [w] as a cover
symbol for the end-point. The lips become increasingly rounding
throughout the diphthong.
In the diphthong [
j], the tongue body begins in the position for [] and moves upwards and
forwards. The lips become increasing less rounded throughout the
diphthong.
In most dialects of English, the vowels we have been transcribing [e]
and [o] also involve an upwards movement of the tongue body. In narrower
transcriptions of these dialects, they would be written [ej] and [ow]:
A tendency to pronounce all tense mid vowels as diphthongs is one of the
most noticeable accent features of English-speakers trying to speak other
languages.
In many dialects, even the vowels we have been transcribing [i] and
[u] have short upwards movements:
