The full form of PhD is Doctor of Philosophy. It is a globally recognized postgraduate academic degree awarded by universities and higher education institutions to a candidate who has submitted a thesis or dissertation, based on extensive and original research in their chosen field. PhD is the highest level of degree a student can achieve in certain fields, such as cognitive psychology, mathematics, English, economics, evolutionary biology, and public health. The specificities of PhD degrees vary depending on where you are and what subject you’re studying. Traditionally, a PhD involves three to four years of full-time study in which the student completes a substantial piece of original research presented as a thesis or dissertation. Some PhD programs accept a portfolio of published papers, while some countries require coursework to be submitted as well.