1. 污迹;污渍
A stain is a mark on something that is difficult to remove.
e.g. Remove stains by soaking in a mild solution of bleach.
用温和的漂白剂浸泡以去除污迹。
e.g. ...a black stain.
黑色污迹
2. 在…上留下污迹;玷污;染污
If a liquid stains something, the thing becomes coloured or marked by the liquid.
e.g. Some foods can stain the teeth, as of course can smoking.
某些食物会在牙齿上留下污渍，吸烟当然也会。