K-9 refers to a variety of entries, most related to dogs. The term originated in the military, where designations such as G-2 are common, making K-9 a rare official pun, being similar to 'canine'.
K-9 is used to refer to police dogs, and is the US military designation for war dogs.
K-9 is the name of several robotic dogs which were characters in the BBC television drama Doctor Who.
