A group of new Ph.D graduates with their professors
A Doctor of Philosophy (PhD,Ph.D., or DPhil; Latinphilosophiae doctorem or doctorem philosophiae) is the highest university degree that is conferred after a course of study by universities in most English-speaking countries. PhDs are awarded for programs across the whole breadth of academic fields. As an earned research degree, those studying for a PhD are usually required to produce original research that expands the boundaries of knowledge, normally in the form of a thesis or dissertation, and defend their work against experts in the field. The completion of a PhD is often a requirement for employment as a university professor, researcher, or scientist in many fields.Individuals who have earned a Doctor of Philosophy degree may, in many jurisdictions, use the title Doctor (often abbreviated "Dr" or "Dr.") or, in non-English-speaking countries, variants such as "Dr. phil." with their name, although the proper etiquette associated with this usage may also be subject to the professional ethics of their own scholarly field, culture, or society. Those who teach at universities or work in academic, educational, or research fields are usually addressed by this title "professionally and socially in a salutation or conversation." Alternatively, holders may use post-nominal letters such as "Ph.D.", "PhD", or "DPhil" (depending on the awarding institution). It is, however, considered incorrect to use both the title and post-nominals at the same time.
The specific 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, or may be granted a master's degree en route to the doctoral degree. Sometimes this status is also colloquially known as "Ph.D. ABD", meaning "All But Dissertation."
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 (iː/). 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.