You must be familiar with expressions like Ah! Oh! etc in English language. Chinese language has similar expressions to indicate different emotions as well. Let’s look at some of them:
哎呀 (āiyā): an expression of wonder, shock, etc.
Āiyā, nǐ wèishéme gàosu tā?
Oh! Why did you tell her?
哎呦 (āiyōu): an exclamation usually indicating disappointment
Āi yōu, wǒ hái méiyǒu zuò gōngkè
Ah! I still haven’t done my homework.
噢 (ō): an expression indicating a sudden realization
Ō, tā shì nǐ dí gēgē
Oh! He is your brother.
Another character, same sound but different tone, can also be used in a similar context:
哦 (ó): an expression to indicate a sudden realization
Ó, shì zhèyàng
Oh! That’s how it is