The University of Sussex defines plagiarism as:
"... the use, without acknowledgement, of the intellectual work of other people, and the act of representing the ideas or discoveries of another as one's own in written work submitted for assessment." The University of Sussex Academic Office, accessed 16th September 2009
It further states that it is an offence for any student to be guilty of, or party to, plagiarism. Academic Misconduct procedures are outlined in the Handbook for Postgraduate External Examiners and Examination Boards and could potentially lead to dismissal from the University.
It is therefore important to ensure that you cite the work of authors you use in a clear and concise manner.
Check the University's Academic Office Website for detailed information.