concordat

n. covenant, agreement (between church and state)

A concordat usually refers to an agreement between the Pope and a government or sovereign on religious matters, although it is also used in relation to some other agreements in internal United Kingdom politics.
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Noun
1. a signed written agreement between two or more parties (nations) to perform some action
(synonym) covenant, compact
(hypernym) written agreement
(hyponym) Lateran Treaty

n. concordat

v. concur, tie in

(n.)
An agreement made between the pope and a sovereign or government for the regulation of ecclesiastical matters with which both are concerned; as, the concordat between Pope Pius VII and Bonaparte in 1801.
  

(n.)
A compact, covenant, or agreement concerning anything.