What is the definition of the marriage contract, when is it written, what are its contents, and are all conditions written in it or are there controls for its contents?

Linguistically, a contract (aqd) is binding and tightening. Technically, it is the binding of the parts of a transaction through offer and acceptance, or the connection of offer with acceptance in a lawful manner that establishes its effect in its proper place. If a contract exists with its conditions, the marriage (nikah) is complete. It is not a condition to write it, document it, or register its terms, as these are additional matters for the purpose of documenting rights and preventing disputes.