Contract (or Contract of Sale): A legally enforceable agreement.

Most of the rules of contract law in Australia come from the common law. Although there are different statutory provisions in each of the States covering various aspects of contracts.

For a contract to be enforceable there must be:

An Offer;
Acceptance;
An intention to enter into the agreement.
Consideration (price); and
The ability to contract.

Some contracts, such as for the sale of land or real estate, must be in writing.