A Primer on Tamil Vowels

Tamil has ten vowels and two diphthongs.

The ten vowels are அ a, ஆ aa, இ i, ஈ ii, உ u, ஊ uu, எ e, ஏ ee, ஒ o, and ஓ oo. You can see (or hear) that they're five distinct sounds, each having a long and short version. Long vowels are "nedil" and short vowels are "kuril". Compare the vowels to "a e i o u" in English.

The two diphthongs are ஐ ai and ஔ au. However, spoken Tamil doesn't really use the diphthongs. Often ஐ ai becomes எ e and ஔ au becomes அவு avu.

So, char siew pau 叉燒包 will be spelled as char siyu pavu சர் சியு பவு instead of char siyu pau சர் சியு பௌ. You'll find au only in a few words like pauttam பௌத்தம் (Buddha) and saukkiyamaa (How are you?, literally "are you well / in good health?").