- A dog’s age: One year in a dog’s life is about 6 to 7 years, so when something has been a dog’s age, it has been a very long time. “I haven’t seen you in a dog’s age” means, “I haven’t seen you in a long time.
- A lucky dog: Some people consider that among all of the animals, dogs (like cats) have been lucky to live with people, so when someone has some good fortune, we say that the person is a lucky dog.
- Working like a dog: In the old days, dogs used to work on farms to help the farmers. And those dogs worked hard. So if a person works very hard, we can say that they work like a dog.
- A dog eat dog world: When an industry is very competitive, like on in the finance world on Wall Street or the entertainment business, we say that it is a dog eat dog world.
- (As) sick as a dog: Dogs, like most animals have some bacteria in their systems. So, we use the phrase sick as a dog or as sick as a dog to mean not feeling very well physically.