Bilaterality (from Latin to " twice," latus "Site") means " two-sidedness ".

In politics, one uses the adjective for bilateral negotiations and agreements, which take place exclusively between two different parties. Bilateral diplomacy is still common in the form of many contracts between two states. Embassies and state visits are mainly used this function.

Also a supranational entity in international law such as the European Union can be a partner for a bilateral agreement; so with the " bilateral agreements between Switzerland and the EU ."

The oldest still into force for Germany bilateral contract is the friendship, trade and navigation treaty between Prussia and the states of the German Customs Union on the one hand and on the other hand Argentina on 19 September 1857.

In economics, the term is used to describe various market forms and their combinations ( monopoly, oligopoly and Polypol ).

In biology, the term used for both sides of the median plane developed organs. Most animals and many plants are constructed bilaterally symmetrical (see: Bilateria ), although there are exceptions to this general rule in some organs.

In anthropology the term is used in relation to kinship. He referred to the situation-dependent reference to either the maternal or paternal relatives.

Related terms are multilateral and unilateral.