开口部

例句：

1. 1. The mouth of the river is wide and deep.
   这条河的口很宽很深。
2. 2. The mouth of the cave was covered in moss.
   洞穴的口被苔藓覆盖。
3. 3. The mouth of the ocean is vast and mysterious.
   海洋的口广阔而神秘。