Of English’s many alternatives to ‘yes,’ the word yeah is perhaps the most common. I’d go so far as to say there is some type of ‘yeah’ or yeah-like word in nearly every native dialect of English. Yet despite its ubiquity, there is something exceptional about ‘yeah,’ namely its curious vowel sound.
Just what is the vowel in ‘yeah?’ In my own accent, I pronounce ‘yeah’ with something like a lengthened, twangy version of the ‘a’ in ‘cat’ (for the IPA-literate, something along the lines of [æə]). So (and forgive the repetition) should we categorize the vowel in ‘yeah’ as the same vowel in ‘cat?’
Probably not. This would break an important rule of American English whereby the short-a in ‘cat,’ ‘trap’ and ‘hat’ cannot occur at the end of word*. And yet if it’s not the ‘short-a,’ then what vowel can we call this?
It might help to look at how ‘yeah’ is pronounced in accents other than my own. In many non-rhotic (i.e. r-less) accents, ‘yeah’ is arguably the same vowel as words like ‘there,’ ‘bear,’ and ‘fair.’ Evidence for this? Some non-rhotic speakers insert a linking-r after ‘yeah’ if it comes before another vowel. I encountered this a mere two days ago, in fact, when an older Rhode Island native said ‘Yeah r it was very nice.’ Ergo, she followed the same set of rules with this sentence as if she were saying ‘There it was very nice.’
Furthermore, in Australian English (and probably several British accents as well), the word seems to undergo a similar shift as ‘fair,’ namely that it becomes a monophthong (a single vowel as opposed to two). Just as an Australian might pronounce ‘square’ as if it were lengthened version of ‘sqweh’ (i.e. [skwe:]), he might also say ‘yeah’ as if it were a lengthened version of ‘yeh’ (i.e. [je:]). So should we treat the ‘yeah’ vowel as the same as the ‘square’ vowel?
There’s a problem here. The vowel I’ve described above (the vowel in ‘square‘) doesn’t really exist in my accent. I pronounce the r in ‘fair,’ so there isn’t any obvious connection to the vowel in ‘yeah.’ Back to square one.
Perhaps ‘yeah’ is simply an anomaly. After all, ‘yes’ variants can be elusive in regards to pronunciation. For example, I answer in the affirmative with several words of the type ‘y___p,’ saying ‘yep,’ ‘yup’ or something in between. Is it pointless to assign ‘yeah’ to a specific type of vowel?
*That is, cannot occur in an open syllable.