Oxford is a collegiate university, consisting of the central University and colleges. The central University is composed of academic departments and research centres, custom writing essay service administrative departments, libraries and museums. The 38 colleges are self-governing and financially independent institutions, which are related to the central University in a federal system. There are also six permanent private halls, which were founded by different Christian denominations and which still retain their Christian character.
The different roles of the colleges and the University have evolved over time.