IAS 37 defines key terms related to contingencies and provisioning. A contingent liability is a possible obligation that arises from past events, while a contingent asset is a possible asset from past events. A provision is a liability of uncertain timing and amount. Legal obligations derive from contracts, legislation or laws, while constructive obligations come from an entity's actions or past practices. An onerous contract is one where costs exceed benefits, and restructuring involves significant changes to a business's scope or operations.