The term COMMON SERVICE DOG can be broken down into three parts: COMMON, SERVICE, and DOG. The first part, COMMON, is defined as something that is shared by all or most members of a group. The second part, SERVICE, refers to the work done by a person or thing for the benefit of others. The third part, DOG, is a domesticated animal that is often kept as a pet. Together, these three words describe a type of DOG that is commonly used to provide assistance to people with disabilities. LAB is a three-letter word that is often used to refer to this type of DOG, as it is short for Labrador Retriever.