Contract, bargain, compact, pact, treaty, entente, convention, cartel, concordat designate an agreement reached after negotiation and ending in an exchange of promises between the parties concerned.
Contract applies especially to a formal written agreement, often of a business nature, couched in such explicit terms as to be enforceable at law.
Bargain applies especially to an agreement regarding purchase and sale.
A compact is an earnest or solemn exchange of promises, sometimes between state or political groups and often between persons. A compact may be unwritten or undocumented, the only assurance of its execution being the trust which each party places in the honor of the other.
The word is used when a keen sense of the obligation which it imposes is assumed of each of the parties.
Pact as used of an agreement between persons or groups is usually interchangeable with compact.
Perhaps because of its popularity with newspaper headline writers which its brevity won for it, pact is used with increasing frequency in the (often unofficial) title of agreements between states; in this use it is frequently interchanged with treaty, which is the generic term for an agreement between states made by negotiation or diplomacy.
Treaty, and never pact, however, is the term for an agreement establishing peace after a period of armed hostility.
An entente is a cordial or amicable agreement between nations in regard to their foreign affairs, usually involving a promise of joint military action in case of aggression against an adherent to the entente.
An entente may be in writing set forth in a published document or it may be based simply on an exchange of promises between heads of government, or may be merely a state of mind of the peoples concerned.
The word is also used of an understanding between groups (as of economic competitors).
A convention is usually an agreement which is either less formal or more specific than a treaty; it may be an agreement between several states regulating matters affecting all of them (as postage, copyright, or the conduct of war) or an agreement between commanders of armies in respect to military operations.
A cartel (see also MONOPOLY) is a written agreeinem or convention between opposing nations, usually for the regulation of intercourse between them in view of or during war.
Cartels provide for such matters as the treatment and exchange of prisoners, postal and telegraphic communication, the mode of reception of bearers of flags of truce, and the treatment of the wounded. Concordat usually applies to an agreement between the pope and a secular government for regulating the relations between church and state.
Less often the term is used for an agreement regulating ecclesiastical matters.