Contract law is based on the principle expressed in the Latin phrase pacta sunt servanda, which is usually translated “agreements must be kept” but more literally means “pacts must be kept”. Contract law can be classified, as is habitual in civil law systems, as part of a general law of obligations.
Jurisdictions vary in their principles of freedom of contract. In common law jurisdictions such as the United Kingdom and the United States, a high degree of freedom is expected. This is in contrast to the civil law, which typically applies certain overarching principles to disputes arising out of contract, as in the French Civil Code or the Iranian. Other legal systems such as Islamic law, socialist legal systems, and customary law have their own variations.
Contracts are widely used in commercial law, and form the legal foundation for transactions across the world. Common examples include construction contract, product purchases (with associated warranties of quality), software licenses, employment contracts, insurance policies, real estate deeds to transfer title, professional services, wholesale merchandise supply, and various other uses.