Alternative dispute resolution or ADR is a name for several dispute resolution processes and techniques which, while believed by some to be outside the traditional mainstream of state jurisprudence, have gained acceptance among both the general public and the legal profession. In this terminology the processes were initially termed "alternative" by twentieth century legal typologists because they were seen as extra-legal supplements to state-sponsored dispute resolution. With the continuing increase in caseload placing great strain on traditional courts, many judges have come to see dispute resolution as an acceptable means of decreasing caseload in traditional courts, while settling disputes in a fair and equitable way. While some would not agree that all alternative methods are always fair and equitable, such methods are much less expensive than a traditional lawsuit.

Arbitration was actually one of the earliest forms of dispute resolution. It was practiced by the jurisconsults of the Roman Empire, and predates the adversarial system of the common law by at least a thousand years. Many people have played the role of mediator, conciliator or arbitrator in many jurisdictions at many times. The Vodun priests of Haiti are well known for their dispute resolution role which occasionally resulted in the losing party being forced to become a zombie. The King of France refused lawyers permission to practice in New France, so Catholic priests and civil law notaries were used by the local populace as dispute resolution resources.

ADR is generally classified into at least three subtypes: negotiation, mediation, and arbitration. (Sometimes a fourth type -- conciliation -- is included as well, but for present purposes it can be regarded as a form of mediation. See conciliation for further details.) The salient features of each type are as follows:

• In negotiation, participation is voluntary and there is no third party who either facilitates the resolution process or imposes a resolution.
• In mediation, participation is voluntary (in that even though a court may mandate the process itself, the parties are not required to reach a resolution), and there is a third party -- a mediator -- who facilitates the resolution process but does not impose a resolution on the parties.
• In arbitration, participation is ordinarily voluntary, and there is a third party who both facilitates the resolution process and imposes a resolution.

To what is "alternative" dispute resolution an alternative? Usually, to litigation -- but more generally, it is also an "alternative" both to allowing a dispute to drop and to resorting to violence. Lawyers have humorous jokes about ADR which use the term as a synonym for any form of violent, extralegal dispute resolution (e.g., my ADR is a two-by-four).

ADR can increasingly be conducted online or by using technology. This branch of dispute resolution is known as Online Dispute Resolution or ODR. It should be noted, however, that ODR services can be provided by government entities, and as such may form part of the litigation process. Moreover, they can be provided on a global scale, where no effective domestic remedies are available to disputing parties, as in the case of the UDRP and domain name disputes. In this respect, ODR might not satisfy the "alternative" element of ADR.

For further details on each subtype, see arbitration, mediation, conciliation, and negotiation. See also Ombudsman.