the sound that people make when they want somebody to repeat something (请对方再说一遍)嗯,什么 the sound that people make when they want somebody to agree or reply (征求对方同意或答复)是吗,好吗,嗯 the sound people make when they are surprised (表示惊奇)啊
Word Originnatural utterance: first recorded in English in the mid 16th cent.