A man was troubled by mice. They ran about all over his house at night. In the daytime, they just stayed under the floor.　　

The man thought, “What I need is a cat, a good cat that can catch mice.” He knew of a man who had cats for sale. So he went to see him. “Do you have a cat that is good for the mice?” he asked the man. “Well, yes. I do happen to have a cat that is good for the mice,” replied the man. “I’ll take it,” said the first man.　　

He paid for the cat and took it home. A week later, he went back again with the cat under his arm. They had a quarrel because they both took the meaning of “good for” as they needed.