改口

to change one's tune / to modify one's previous remark / to change the way one addresses sb (as when one marries and starts to call one's husband's parents 爸爸[ba4 ba5] and 媽媽|妈妈[ma1 ma5])

mouth / classifier for things with mouths (people, domestic animals, cannons, wells etc) / classifier for bites or mouthfuls

to change / to alter / to transform / to correct

a gift of money given by parents on both sides after a wedding, to their new daughter-in-law or son-in-law