A ketric was a measurement of distance used by the Hirogen, roughly equivalent to the sensor range of the USS Voyager.
In 2374, a Hirogen ship detected the USS Voyager as being four thousand ketrics away from a module of the Hirogen communications network. (VOY: "Hunters")
The Star Trek Encyclopedia, 4th ed., vol. 1, p. 414 stated that a ketric was equivalent to several kilometers.