A doctorate can be an academic degree or a professional degree. In addition to the PhD there are a number of other doctorates, perhaps not as well-known, but just as prestigious. As a prospective student, you may have to make a decision between a PhD or a 'professional' or 'practice' doctorate, depending on your experience, subject area, or career ambitions.
More information on professional doctorates is available here. Below is a short summary of the range of doctorates you may find around the world to help you with your initial investigations.
There are three types of doctorates: equivalent to PhD, Professional Doctorates and Higher degrees.
There are several degrees which are equivalent to a PhD but have a different title, such as:
All of the above are academic research degrees equivalent to a UK PhD. It gets complicated because some of these degree titles, such as the Doctor of Science, can be used in other countries to designate 'higher degrees'. Higher degrees (see below), are awarded in recognition of a significant and original contribution to knowledge over a sustained period. Work submitted for a higher degree is expected to be of international calibre (University of Edinburgh definition).
The term 'professional doctorate' is itself a matter of debate. These doctorates can also be referred to as taught, by practice or industrial.
There are broadly two types of 'professional' doctorates:
Numerous fields of study, notably (but not exclusively) medicine and allied health professions have professional doctorates. For example; those working in dentistry, optometry, pharmacy, psychology, physical therapy, occupational therapy, and health science usually require such degrees for professional registration.
A professional development qualification will provide the holder with the ability to apply for more senior positions in their field, as well as in academia, but is not necessarily required for professional registration such as Doctorate of Education (EdD).
Professional doctorates have been around in the UK since the early 1990s, although some more established doctoral programmes have also been brought under the professional doctorate umbrella. The aim of these programmes is to find novel approaches to integrating professional and academic knowledge. According to the UK Economic & Social Research Council (ESRC), students undertaking a professional doctorate are expected to:
".... make a contribution to both theory and practice in their field, and to develop professional practice by making a contribution to (professional) knowledge."
There is a good definition comparing industrial PhDs and EngD on the website of the Centre for Innovation Manufacturing in Composites at the University of Nottingham:
“PhD research can vary from abstract/theoretical to applied industry research. EngD research usually concerns a topic related to the business activities of the industrial sponsor. All time spent on EngD programmes are recognised by relevant institutions as contributing towards Chartered Engineer (CEng) status.”
The EngD is mainly a UK doctorate, but there are similar doctorates such as the European Industrial Doctorate (funded by the European Commission Marie Curie Actions). EIDs are joint-doctoral training projects between an academic participant and a company established in two different EU Member States.
Creative PhDs can be awarded by practice, portfolio or composition in disciplines which include music, film, theatre, architecture or design. These degrees are called 'Doctor of Arts' in the USA and Canada.
They generally carry additional requirements (University of East Anglia definition):
Higher degrees are awarded in recognition of a substantial body of original research undertaken over the course of many years over and above that of a PhD.
Typically, the candidate will submit a collection of work which has been previously published in a peer-refereed context and pay an examination fee. The university assembles a committee of academics, both internal and external; who review the work submitted and decide whether the candidate deserves the doctorate based on the submission. It is not to be mixed up with the standard PhD requirements in the Netherlands (which tends to consist of thesis made up of three or four papers, minimum).
Most universities restrict candidacy to graduates or academic staff of several years standing. The most common doctorates of this type are those in Divinity (DD), Law (LLD), Civil Law (DCL), Music (DMus or MusD), Letters (DLitt or LittD), Science (DSc or ScD) and DSc (Med). Some institutions may also award a doctorate by publication to individuals fulfilling the conditions above, but who do not have a PhD already.
In some European countries like Germany, such an award (also called habilitation or Privatdozent) is used during recruitment of senior academics to demonstrate independent and thorough research, experience in teaching and lecturing and, more recently, the ability to generate funding within the area of research.
Higher degrees are often awarded honoris causa (the usual requirements, such as matriculation, residence, study and the passing of examinations, are waived) and are known as honorary degrees.