The Collaborative International Dictionary of English v.0.48:

Knife \Knife\ (n[imac]f), n.; pl. Knives (n[imac]vz). [OE.
   knif, AS. cn[imac]f; akin to D. knijf, Icel. kn[imac]fr, Sw.
   knif, Dan. kniv.]
   1. An instrument consisting of a thin blade, usually of steel
      and having a sharp edge for cutting, fastened to a handle,
      but of many different forms and names for different uses;
      as, table knife, drawing knife, putty knife, pallet knife,
      pocketknife, penknife, chopping knife, etc..
      [1913 Webster]

   2. A sword or dagger.
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            The coward conquest of a wretch's knife. --Shak.
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   Knife grass (Bot.) a tropical American sedge (Scleria
      latifolia), having leaves with a very sharp and hard
      edge, like a knife.

   War to the knife, mortal combat; a conflict carried to the
      last extremity.
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The Collaborative International Dictionary of English v.0.48:

Knives \Knives\,
   n. pl. of Knife. See Knife.
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The Collaborative International Dictionary of English v.0.48:

Pocketknife \Pock"et*knife`\, n.; pl. -knives.
   A knife with one or more blades, which fold into the handle
   so as to admit of being carried in the pocket.
   [1913 Webster]