The Collaborative International Dictionary of English v.0.48:

Negligence \Neg"li*gence\, n. [F. n['e]gligence, L.
   negligentia.]
   The quality or state of being negligent; lack of due
   diligence or care; omission of duty; habitual neglect;
   heedlessness.
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   2. An act or instance of negligence or carelessness.
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            remarking his beauties, . . . I must also point out
            his negligences and defects.          --Blair.
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   3. (Law) The omission of the care usual under the
      circumstances, being convertible with the Roman culpa. A
      specialist is bound to higher skill and diligence in his
      specialty than one who is not a specialist, and liability
      for negligence varies acordingly.
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   Contributory negligence. See under Contributory.
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   Syn: Neglect; inattention; heedlessness; disregard; slight.

   Usage: Negligence, Neglect. These two words are freely
          interchanged in our older writers; but a distinction
          has gradually sprung up between them. As now generally
          used, negligence is the habit, and neglect the act, of
          leaving things undone or unattended to. We are
          negligent as a general trait of character; we are
          guilty of neglect in particular cases, or in reference
          to individuals who had a right to our attentions.
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The Collaborative International Dictionary of English v.0.48:

Contributory \Con*trib"u*to*ry\, a.
   Contributing to the same stock or purpose; promoting the same
   end; bringing assistance to some joint design, or increase to
   some common stock; contributive. --Milton.
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         Bonfires of contributory wood.           --Chapman.
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   Contributory negligence (Law), negligence by an injured
      party, which combines with the negligence of the injurer
      in producing the injury, and which bars recovery when it
      is the proximate cause of the injury. --Wharton.
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WordNet (r) 3.0 (2006):

contributory negligence
    n 1: (law) behavior by the plaintiff that contributes to the
         harm resulting from the defendant's negligence; "in common
         law any degree of contributory negligence would bar the
         plaintiff from collecting damages"