Minor: Person under the age of 18 who is not married (or has not been married). A minor may only enter into certain contracts, such as those for necessaries or an apprenticeship. A Irish resident under the age of 18 may not legally marry, even if the ceremony takes place in a place (such as Northern Ireland) where the minimum age for marriage is under 18.

Misfeasance: Improperly doing something which a person has a legal right to do. Contrast with nonfeasance.

Misjoinder: When a person has been wrongly named as a party to a law suit, a court will usually amend the proceedings to strike out the name of the misjoined party and substitute the person who should have been joined.

Misrepresentation: False material statement which induces a party to enter into a contract grounds for rescission of the contract.

Mitigation: Facts which, while not negating an offence or wrongful action, tend to show that the defendant may have had some excuse for acting the way he did. For example, provocation may constitute mitigating circumstances in an assault action.

Mitigation of damages: A person who sues another for damages has a duty to minimize his loss, as far as reasonable. For example, in a wrongful dismissal suit, the person who was fired should make some effort to find another job, to minimize the economic damage to himself.