Unilaterale

Unilaterale is an adjective used in several languages, notably Italian and German, to describe actions, obligations, or conditions that originate from or affect only one party or one side. The word derives from uni- meaning one and lateral meaning side. In international law and politics, a unilateral action is taken by a single state or actor without requiring or seeking agreement from others. Such actions can take the form of declarations, sanctions, recognitions, or policy measures. Unilateral measures may be binding within the adopting state and can have various legal effects domestically, but they often raise questions of legitimacy and coordination with other actors, and they may be offset by reciprocal or multilateral responses. In diplomacy, unilateralism refers to a preference for acting alone rather than through alliances or multilateral institutions.

In contract law, a unilateral contract is formed when one party promises to pay or perform in response to the other party's conduct, such as offering a reward for a lost item. Acceptance is typically through performance rather than a promise.

In medicine and anatomy, unilateral describes something affecting only one side of the body, such as unilateral headache or unilateral deafness. The term contrasts with bilateral, which involves both sides.

Unilaterale usage emphasizes single-party origin or impact, though the term appears across legal, political, medical, and everyday contexts. Related terms include bilateral, multilateral, and unilateralism.