A dog is a very common four-legged animal that is often kept by people as a pet or to guard or hunt. There are many different breeds of dog.

You use dog eat dog to express your disapproval of a situation where everyone wants to succeed and is willing to harm other people in order to do so.

If you say that something is going to the dogs, you mean that it is becoming weaker and worse in quality.

If problems or injuries dog you, they are with you all the time.