Ⅰ. mouse “老鼠、耗子”，比rat 小。如：
① I have set a trap for mouse. 我装置了一个捕鼠器捕鼠。
② When the cat’s away, the mice will play. ：猫儿一跑耗子闹。
Ⅱ. rat “老鼠、耗子”，比mouse 大。如：
① A rat has fallen into the trap. 一只老鼠落到了捕鼠器里。
② A rat crossing the street is chased by all. 老鼠过街，人人喊打。