Tort law: Negligence - Entrustment / Liability torts - Quasi-tort & Ultrahazardous activity

Negligent entrustment is a cause of action in tort law that arises where one party (the entrustor) is held liable for negligence because they negligently provided another party (the entrustee) with a dangerous instrumentality, and the entrusted party caused injury to a third party with that instrumentality. The cause of action most frequently arises where one person allows another to drive their automobile.

Quasi-tort is a legal term that is sometimes used to describe unusual tort actions, on the basis of a legal doctrine that some legal duty exists which cannot be classified strictly as negligence in a personal duty resulting in a tort nor as a contractual duty resulting in a breach of contract, but rather some other kind of duty recognizable by the law. It has been used, for example, to describe a tort for strict liability arising out of product liability, although this is typically simply called a 'tort'.

Although it is not to be found in most legal dictionaries, it has been used by some scholars such as Sri Lankan Lakshman Marasinghe. Lakshman proposes that the doctrine provides legal relief that falls outside tort or contract, but with some of the characteristics of tort or contract, as can be found in restitution (including unjust enrichment), equity (including unconscionable conduct), beneficiaries under a trust of the benefit of a promise, people protected by the valid assignment of promise, fiduciary duty, and contracts of insurance.

An ultrahazardous activity in the common law of torts is one that is so inherently dangerous that a person engaged in such an activity can be held strictly liable for injuries caused to another person, even if the person engaged in the activity took every reasonable precaution to prevent others from being injured. In the Restatement of the Law 2d, Torts 2d, the term has been abandoned in favor of the phrase "inherently dangerous activity."