The requirements to earn a PhD degree vary considerably according to the country, institution, and time period, from entry-level research degrees to higher doctorates. During the studies that lead to the degree, the student is called a doctoral student or PhD student; a student who has completed all of their coursework and comprehensive examinations and is working on their thesis/dissertation is sometimes known as a doctoral candidate or PhD candidate (see: all but dissertation). A student attaining this level may be granted a Candidate of Philosophy degree at some institutions.
A PhD candidate must submit a project, thesis or dissertation often consisting of a body of original academic research, which is in principle worthy of publication in a peer-reviewed journal. In many countries, a candidate must defend this work before a panel of expert examiners appointed by the university. Universities sometimes award other types of doctorate besides the PhD, such as the Doctor of Musical Arts (D.M.A.) for music performers and the Doctor of Education (Ed.D.) for professional educators. In 2005 the European Universities Association defined the Salzburg Principles, ten basic principles for third-cycle degrees (doctorates) within the Bologna Process. These were followed in 2016 by the Florence Principles, seven basic principles for doctorates in the arts laid out by the European League of Institutes of the Arts, which have been endorsed by the European Association of Conservatoires, the International Association of Film and Television Schools, the International Association of Universities and Colleges of Art, Design and Media, and the Society for Artistic Research.
In the context of the Doctor of Philosophy and other similarly titled degrees, the term "philosophy" does not refer to the field or academic discipline of philosophy, but is used in a broader sense in accordance with its original Greek meaning, which is "love of wisdom". In most of Europe, all fields (history, philosophy, social sciences, mathematics, and natural philosophy/sciences) other than theology, law, and medicine (the so-called professional, vocational, or technical curriculum) were traditionally known as philosophy, and in Germany and elsewhere in Europe the basic faculty of liberal arts was known as the "faculty of philosophy".
The degree is abbreviated PhD (sometimes Ph.D. in North America), from the Latin Philosophiae Doctor, pronounced as three separate letters (//). The abbreviation DPhil, from the English 'Doctor of Philosophy', is used by a small number of British and Commonwealth universities, including Oxford and formerly York and Sussex, as the abbreviation for degrees from those institutions.
In the universities of Medieval Europe, study was organized in four faculties: the basic faculty of arts, and the three higher faculties of theology, medicine, and law (canon law and civil law). All of these faculties awarded intermediate degrees (bachelor of arts, of theology, of laws, of medicine) and final degrees. Initially, the titles of master and doctor were used interchangeably for the final degrees—the title Doctor was merely a formality bestowed on a Teacher/Master of the art—but by the late Middle Ages the terms Master of Arts and Doctor of Theology/Divinity, Doctor of Law, and Doctor of Medicine had become standard in most places (though in the German and Italian universities the term Doctor was used for all faculties).
The doctorates in the higher faculties were quite different from the current PhD degree in that they were awarded for advanced scholarship, not original research. No dissertation or original work was required, only lengthy residency requirements and examinations. Besides these degrees, there was the licentiate. Originally this was a license to teach, awarded shortly before the award of the master or doctor degree by the diocese in which the university was located, but later it evolved into an academic degree in its own right, in particular in the continental universities.
According to Keith Allan Noble (1994), the first doctoral degree was awarded in medieval Paris around 1150. The doctorate of philosophy developed in Germany as the terminal Teacher's credential in the 17th century (c. 1652). There were no PhDs in Germany before the 1650s (when they gradually started replacing the MA as the highest academic degree; arguably one of the earliest German PhD holders is Erhard Weigel (Dr. phil. hab., Leipzig, 1652).