1.You can never teach an old dog new tricks. 老古董學不會新東西
You're never going to teach your father at the age of 79 to use a computer. You can't teach an old dog new tricks, you know.
不要指望教你79歲的老父親學會電腦。年長的人學不會新事物。

2.meaner than a junkyard dog 冷漠，不友好
He is a man meaner than a junkyard dog.
他是一個殘酷、冷漠的男人。

3.His bark is worse than his bite. 刀子嘴、豆腐心
I wouldn't be scared of her if I were you. Her bark's a lot worse than her bite.
如果我是你，我不會怕她。她是個刀子嘴，豆腐心的人。

4.let sleeping dogs lie 不要自找麻煩、自討苦吃
Green is trying to let sleeping dogs lie.
格林在努力避免招惹是非。

5.the dog days of summer 一年中最熱的三伏天
I can do nothing except for swimming in the dog days of summer.
在三伏天里，除了游泳，我什么事也做不成。

6.to rain cats and dogs 下傾盆大雨
In the middle of the picnic it started to rain cats and dogs, and everybody got soaked.
野餐進行到一半時，天開始下起大暴雨，每個人都濕透了。