aha
Very common
Interjection
Register:neutral
Function:response, surprise
Strength:normal
Position:initial
Punctuation:comma/parenthetical
Reduplication allowed:No
Examples
Aha, I understand it now.
Aha, that is your bag.
Aha, that is why you are waiting here.
Aha, today is Friday.
Aha, so we will go home.