A knife is a metal tool with a sharpened metal blade that is used to cut all sorts of things. The plural form of "knife" is "knives." Knives can serve various purposes. Hunters use a hunting knife, soldiers use the combat knife, scouts, campers, and hikers carry a pocketknife; there are kitchen knives for preparing foods, table knives, weapons, knives for throwing or juggling, and knives for religious ceremony or display.