um
exclamation uk/əm/ us/əm/
呃，嗯（表示说话中间停顿或考虑下文的象声词）
used in writing to represent the sound that people make when they are pausing or deciding what to say next
"What do you think of this jacket?" "Um, I don't know if I like the colour." “你觉得这件夹克怎么样？”“呃，我不知道是否喜欢这种颜色。”
"So what did you talk about?" "Um, I don't remember." “那么你们谈了些什么？”“嗯，我不记得了。”