A more thorough explanation:

Definition: To put an animal to death by euthanasia.

Example: The veterinarian had to euthanize the dog because it was suffering from a terminal illness and was in a lot of pain.

Explanation: Euthanize is a term used when an animal is put to death in a humane way, usually to end their suffering. In the example, the dog was euthanized because it was in pain and had no chance of recovery. This is a common practice in veterinary medicine when an animal's quality of life is severely compromised.