What is the difference between purchasing and supply management?

Purchasing is a functional group that is in charge of the selecting, evaluating, negotiating, buying goods and services to maximise value of the organisation. The supply management on its side deals with a strategic approach. It identifies the requirements of its internal customers (e.g. the requirement from engineering, marketing etc) and acquire those requirements by the effective management of the supply base with the help of cross-functional teams to achieve organizational goals.