Confusingly, the terms dissertation and thesis are often used interchangeably within higher education and university environments (or graduate school in the USA). Depending on the context, someone may refer to a project write-up as a thesis while another person may call the same document a dissertation. In another scenario, both terms may refer to very specific and different things. If we look at the meaning of ‘dissertation’ and ‘thesis’ in the Cambridge English Dictionary, we find their definitions to be:
The dictionary definitions of these two words are almost identical. The difference is in the detail: a thesis is ‘especially’ for a higher degree, such as a PhD. The same dictionary’s American entry shows how the words shift across the Atlantic, defining a dissertation as:
Dissertation vs thesis at a glance
| UK usage | US usage | |
|---|---|---|
| PhD document | Thesis (Imperial, Manchester and University of London regulations) | Often dissertation (for example Harvard), though some universities, such as MIT, say thesis |
| Bachelor’s or master’s project | Can be called a dissertation (for example Edinburgh’s MSc in Operational Research) | Can be called a thesis (MIT uses ‘thesis’ for master’s degrees) |
| Length examples | Master’s: Edinburgh’s MSc in Operational Research expects 10,000 to 14,000 words. PhD: 80,000 words of main text at Manchester; 100,000 words at Nottingham and the University of London | Set by each university and department |
| Original research required? | PhD: yes, an original contribution to knowledge (QAA). Master’s: depends on the course | Set by each university |
| Oral exam? | PhD: yes, a viva with at least one external examiner (QAA). Master’s: depends on the course | Set by each university |
The sources for each point are named in the sections below; all were checked on 20 October 2026.
Dissertation vs thesis in the UK
The British dictionary definitions above sum up how the two terms tend to be used in the UK. You may write a dissertation for an undergraduate or master’s degree, whilst if you continue to a PhD, you’ll be writing up a thesis.
The distinction here is that a PhD (also referred to as a doctoral degree) requires an original contribution to knowledge: the Quality Assurance Agency (QAA) says every UK doctorate must demonstrate ‘an original contribution to knowledge in their subject, field or profession’. A taught master’s project follows a period of taught modules and does not have to meet that doctoral test; depending on the course, it could even consist mainly of a review of existing research literature.
A well-written dissertation project as part of a master’s degree would be closer in length and format to a research paper than to a PhD thesis.
Imperial College London is a good example of an institution where the term for research degrees is clear: students on its research degrees submit a PhD, MPhil, MD(Res) or EngD thesis. At the University of Edinburgh, for example, MSc Operational Research students submit a dissertation, which is read by two internal examiners and reviewed by the External Examiner.
As part of a doctoral degree, you may also write research papers which go through peer review, and these can strengthen your thesis. Papers can come out of a master’s project too; if that is your aim, plan it with your supervisor from the start.
A structural difference between the two is scale. A master’s dissertation might be built around one main research question, whereas a PhD thesis may give each chapter its own study or research question.
A master’s degree can be a good way to develop basic research skills such as how to critically review existing literature and previously published papers. You’ll get a sense of what independent research is like and how to formulate a research plan. On a taught master’s you may also submit coursework across the year, as well as the final dissertation.
The difference here is that whilst you may perform your research, data collection and writing across several months for a master’s project, your PhD thesis work will take much longer, and ideally you should be working towards your thesis writing over much of the three or more years of your project.
Finding a PhD has never been this easy – search for a PhD by keyword, location or academic area of interest.
Dissertation vs thesis in the USA
In the United States the naming convention is not used in the same way, and it varies between universities.
The key thing to be aware of is that at some US graduate schools the definitions are essentially reversed. At Harvard’s Graduate School of Arts and Sciences, for example, ‘PhD candidates must successfully complete and submit a dissertation to qualify for degree conferral’. A master’s degree may instead involve a thesis. There are exceptions, though: MIT uses ‘thesis’ for both, stating that ‘master’s and doctoral theses must be submitted electronically’. If you are applying to or studying at a US university, use the term in your own programme’s handbook.
Dissertation vs thesis: the similarities
Regardless of the precise term used to describe the body of academic work you produce, both are substantial written documents, but the lengths are very different. A taught master’s dissertation may be 10,000 to 14,000 words (the expectation for Edinburgh’s MSc in Operational Research), while a PhD thesis can run to several times that: the University of Manchester sets a limit of 80,000 words of main text, and the University of Nottingham and the University of London allow up to 100,000 words. Our guide to how long a PhD thesis is has more detail.
If you want to see what finished theses look like, you can browse theses by department in Warwick’s research archive (WRAP).
Some element of research work and independent learning will be key to both. For a PhD, though, the research is the core focus that the work is centred on, whilst a master’s (or undergraduate) project will vary in how much original research it involves.
The way they are examined differs too. A UK PhD thesis is examined at an oral examination, the viva, and the QAA says at least one external examiner is required at each one. Whether a master’s dissertation has an oral examination depends on the course: the page describing how Edinburgh’s MSc Operational Research dissertations are assessed mentions examiners reading the dissertation, and no viva.
Conclusion
The confusion between the precise meaning of thesis and dissertation is completely understandable: the dictionary definitions are very similar, and the words are used differently depending on what part of the world you’re in. Both require a substantial amount of academic writing and form part of a degree, whether a PhD or a master’s.
As I’m in the UK, I’ll conclude by saying that a dissertation is typically associated with the work of an undergraduate or master’s degree, whilst a thesis is written as part of a research project leading to the award of a PhD or an equivalent research degree.
See below for a recap of answers to common questions about the differences between a dissertation and a thesis.
Can you convert a dissertation or thesis into a research paper?
You should be able to write up the work presented in either document as a research paper, or even several papers. You stand a better chance of making it through peer review if your research contributes new knowledge to the subject. This is possible at master’s level, and the University of London’s regulations expect a PhD thesis to be of a standard to merit publication. An undergraduate dissertation can lead to a paper too, especially if this was planned before starting the project. Our guide to turning a thesis into a paper explains the process.
What degree would you write a dissertation or thesis for?
In UK usage, a thesis is associated especially with a higher degree, so you would write a thesis for a PhD or other research degree, and a bachelor’s or master’s project can be called a dissertation. In the US, a PhD may end with a dissertation (as at Harvard), so check the term your university uses.
Do you have a viva after submitting a dissertation or thesis?
For a UK PhD, yes: the thesis is examined at a viva, an oral examination at which you defend your work. For a master’s dissertation, it depends on the course, so check your programme handbook. Our guide to the PhD viva explains what happens and how to prepare.
Do you have to do a literature review as part of a dissertation or thesis?
Expect to review the literature in some form. The main difference is scale: in a PhD thesis, the literature review can be a standalone chapter, while in a shorter dissertation it may be a section of the introduction. Ask your supervisor what is expected for your course.
