the phd/dphil degree usually takes between three and six years of full-time study to complete. they may or may not require a master's degree beforehand. many phd/dphil degrees begin with a period of graduate courses. after the phd/dphil student has taken these courses, they take examinations to test what the student knows about their area of study. after the student passes the exams, they begin to do original research. the product is a long research report called a dissertation (or a "thesis"). some phd/dphil degrees also require students to pass exams in languages (such as french, german, or other languages). many phd/dphil students teach undergraduate students or assist professors with research during their phd/dphil studies.