K9 or K-9 is a term used to refer to police dogs and the police dog unit itself. The term is derived from the English and French word "canine," which simply means "dog". Police dogs are specifically trained to assist members of law enforcement in various duties such as search and rescue, detection of narcotics or explosives, and suspect apprehension. German Shepherds and Belgian Malinois are the most commonly used breeds for police dogs, but other breeds such as Basset Hounds, Bloodhounds, and Labrador Retrievers are also used for their tracking, trailing, and detection skills. Police K-9s usually serve in the force for 6 to 9 years. Police departments require a dog to first pass basic obedience training, and there are two common classifications of police K-9s: patrol and detection. Patrol dogs are used to provide patrol duties such as officer protection, suspect apprehension, area or building clearance, and security in sensitive or controlled areas. Detection dogs are used to find either narcotics or explosives. Police dogs are trained to follow both verbal and hand commands of their handler.