|Part of the common law series|
|Liability and remedies|
|Duty to visitors|
|Other common law areas|
Comparative negligence, or non-absolute contributory negligence outside of the United States, is a partial legal defense that reduces the amount of damages that a plaintiff can recover in a negligence-based claim based upon the degree to which the plaintiff's own negligence contributed to cause the injury. When the defense is asserted, the fact-finder, usually a jury, must decide the degree to which the plaintiff's negligence versus the combined negligence of all other relevant actors contributed to cause the plaintiff's damages. It is a modification of the doctrine of contributory negligence which disallows any recovery by a plaintiff whose negligence contributed, even minimally, to causing the damages.
Prior to the late 1960s, however, only a few states had adopted this system. When comparative negligence was adopted, three main versions were used. The first was called "pure" comparative negligence. A plaintiff who was 90% to blame for an accident could recover 10% of his losses. (Of course, if the defendant suffered injuries in such a case, he/she could counter claim and recover 90% of his/her losses from the other party.)
The second and third versions are lumped together in what is called "modified" comparative negligence. One variant allows plaintiffs to recover only if the plaintiff's negligence is "not greater than" the defendant's (viz., the plaintiff's negligence must not be more than 50% of the combined negligence of both parties).
The other variant allows plaintiffs to recover only if the plaintiff's negligence is "not as great as" the defendant's (viz., the plaintiff's negligence must be less than 50% of the combined negligence). The apparently minor difference between the two modified forms of comparative negligence are thought by lawyers handling such cases to be significant in that juries who ordinarily assign degrees of fault are much less willing to award damages to a plaintiff who is equally at fault than to one who is less at fault than the defendant.
Contributory negligence doctrine 
Some states, though, still use the contributory negligence doctrine when evaluating negligence in a tort. Alabama, for instance, has not adopted this. In Williams v. Delta Int'l Machinery Corp., 619 So.2d 1330, 1333 (Ala. 1993), the court said: "[after] exhaustive study and these lengthy deliberations, the majority of this Court, for various reasons, has decided that we should not abandon the doctrine of contributory negligence, which has been the law in Alabama for approximately 162 years." Maryland, North Carolina, Virginia, and Washington, D.C. continue to use contributory negligence as well.
Neither comparative negligence nor contributory negligence should be confused with joint and several liability which generally holds each of two or more culpable defendants responsible for all the damages sustained by a plaintiff. For practical reasons, a plaintiff who faces the defense of comparative negligence may wish to join all potentially culpable defendants in his action because the plaintiff's negligence will be balanced against the combined negligence of all defendants in apportioning damages, even though the plaintiff may not be able actually to get compensation from some of them--for example where an insolvent individual and a major corporation were both negligent in causing plaintiff's harm.