呀 and 啊 both seem to be used in the end of sentences for exclamation, and the only difference that I can think of is that the pronunciation in Putonghua (Mandarin) is different. In Cantonese, even the pronunciation is the same. Do 呀 and 啊 mean the same thing and can be used interchangeably or are their meaning different?
see grammars or dictionaries, e.g.＂汉语８００虚词用法词典＂：呀［助］（aux。）used in place of 啊 when the preceding character ends in the sound a,o,e,i,or v (u umlaut) 是＂啊＂受前一字韵母a,o,e,i，v 的影响而发生的音变。– user6065Mar 3, 2018 at 13:41
Reading all the questions here makes me doubt whether I am really a Chinese. I have never thought about this before. :-)– Yu ZhangMar 3, 2018 at 16:19
ABC's entry for 呀 says:
(replacing a (啊) when preceding word ends in a, e, i, o, or (y)u)
快来呀! Kuài lái ya! Come quickly!
呀 is a replacement for 啊 when it comes after a vowel.
This is also corroborated by《规范》's entry:
说话(huà)呀 | 车(chē)呀 | 你说(shuō)呀 | 起来(lái)呀 | 快去(qù)呀。
It's a hard question.
They are interchangeable most of time in this usage without affecting meaning. I can't think of an example in which you can only use one over the other.
To me, 呀 sounds more folksy, while 啊 sounds a bit more formal.
The simplistic way to remember it is: they are various forms of 啊 depending on (the shape of the mouth in) the ending sound of the previous syllable. There're also 哪 which is 啊 preceded by a final n-sound (人哪 Oh people!); 哇 (好哇；不够哇);啦 (preceded by 儿 sound in Northern-speak)；etc.
However, there is still a difference between them in some cases (need more context), sometimes conveying surprise, disbelief, amazement, etc.