This is the 6210th most frequent Chinese word.
开口
To begin speaking or open one's mouth to talk.
Here '开口' means 'to start speaking' or 'to open one's mouth.' It suggests the act of beginning to talk, often emphasizing the effort or hesitation involved.
他说话从不轻易开口。
He rarely opens his mouth to talk.
In this sentence, '开口' refers to 'an opening' or 'gap' through which something can pass. It is used to describe a physical gap or opening.
窗户开口处有冷风进来。
Cold wind is coming in from the window opening.
Here '开口' is used in a figurative sense, meaning 'to start smiling or laughing.' It emphasizes the joyful immediate reaction.