interjection · interjection indicating that one has just learned something

哦，我明白了。

interjection, modal particle, punctuation · sentence-final particle conveying informality, warmth, friendliness, or intimacy

没问题哦。

interjection · oh (interjection indicating doubt or surprise)

哦？你确定这是他做的吗？

verb · to chant

他在书斋里吟哦唐诗。