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What’s the Difference between a Dissertation and a Thesis

Dr Harry Hothi
Dissertation versus Thesis
At universities in the UK, a dissertation, usually around 20,000 words is written by undergraduate and Master’s students, whilst a thesis, around 80,000 words, is written as part of a PhD. In the USA, these definitions of dissertation and thesis are usually reversed

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 take a look at the meaning of dissertation’ and thesis’ in the Cambridge English Dictionary, we find their definitions to be:

Definition of Dissertation
“a long piece of writing on a particular subject, especially one that is done in order to receive a degree at college or university”.
Definition of Thesis
“a long piece of writing on a particular subject, especially one that is done for a higher college or university degree”.

The dictionary definitions of these two words are almost identical! Technically and historically this has been the correct however if we look at the definition of ‘dissertation’ and ‘thesis’ in the Collins English Dictionary, we start to get a sense of the modern interpretation of the two words, particularly as they’re used in the United Kingdom:

Definition of Dissertation
“…a long formal piece of writing on a particular subject, especially for a university degree”.
Definition of Thesis
“…a long piece of writing based on your own ideas and research that you do as part of a university degree, especially a higher degree such as a PhD”.

Dissertation vs Thesis – the UK

The definition above succinctly sums up the differences between the terms dissertation and thesis in the UK and much of Europe. Most often students will be asked to write an undergraduate or Master’s dissertation whilst if you continue on to in to a PhD doctoral program, you’ll be writing up a thesis.

The distinction here is that a PhD (also referred to as a doctoral degree) requires the development of a novel body of work that adds new knowledge based purely on original research, whilst an undergraduate or Master’s project follows a period of taught modules and does not require novel research; for example it could consist solely of a review of existing research literature.

A well written dissertation project as part of a Masters degree would be closer in length and formatting to a research paper.

Imperial College London is a good example of an institution where this distinction between the terms is clear; the terminology used for students undertaking original research degrees is that they will be asked to submit a PhD, MPhil, MD(Res) or EngD thesis. Conversely, students enrolled in a taught Masters postgraduate degree are asked to submit Master’s dissertations.

As part of a doctoral degree, it’s also common to write research papers which go through a peer review process and help make your thesis defence that much easier. Publishing papers during a Masters degree is less common (but not impossible) than with a doctorate degree, simply because the emphasis with these is less on performing original research/contributing new knowledge, but more on equipping a student with the ability to do so in the future (i.e if they do eventually pursue a PhD degree).

An important structural difference between the two is that the Masters dissertation structure is usually centred around one primary research question whereas a Ph.D. is likely to contain each chapter to a separate research topic and research methodology.

A Masters 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. You’ll be required to submit coursework or another written report format on a given topic throughout the year, in addition to the final 10,000-20,000 word dissertation.

The difference here is that whilst you may perform your subject research, data collection and writing across several months for a Masters project, your PhD thesis work will take much longer. Your data collection alone for doctoral study can take in excess if two years and ideally you should be working towards your thesis writing over much of the three years of your project.

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Dissertation vs Thesis – the USA

Whilst this naming convention in the UK and the rest of Europe is used consistently across the vast majority of universities and departments, this is not necessarily the case at graduate schools in the United States of America.

The key thing to be aware of is that in the USA, the definitions are essentially reversed; a Masters degree in the United States is earned following the completion and submission of a Master thesis, whilst a doctoral dissertation is written by a graduate student as part of the journey towards a PhD degree.

Dissertation vs Thesis – the Similarities

Regardless of the precise term used to describe the body of academic work you produce, both of these will be substantial written documents. They will range in length from around 20,000 word dissertation for a Masters degree project write up, to over 50,000 words for a PhD submission; a 100,000 word thesis is usually the maximum permitted by most universities.

Click here to view PhD thesis examples that have been made available online by the University of Warwick

Some element of research work and independent learning will be key to both, however of course for PhDs, the research element will be the core focus that the work is centred on whilst the Maser’s (or undergraduate) project will have flexibility as to the extent of research work conducted.

Both a thesis and dissertation will conclude with the student taking part in a viva to defend the work of their research project. A dissertation defence for a masters degree will involve at least one faculty member and the student. A doctoral candidate will on the other hand have their thesis defense with at least one external examiner.


The confusion for students between the precise meaning of the term thesis and dissertation is completely understandable; this is due to the very similar dictionary definitions of the words combined with the different context they can refer to depending on what part of the world you’re in. Both require a substantial amount of academic writing, forming part of a graduate program to earn the academic degree of a PhD or Masters.

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 degree or an equivalent research degree.

See below for a recap of answers to common questions about the differences between the a dissertation and thesis.

Can you convert a dissertation or thesis into a research paper?

Theoretically 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 work contributes new knowledge to the subject matter. This is certainly possible at the Masters level and essential for a doctorate program. An undergraduate dissertation is less likely to lead to an academic paper unless this is something that has specifically been planned for before starting the project.

What degree program would you write a dissertation or thesis for?

Both documents are written at the graduate level. In the UK, a dissertation is written at the Masters levels whilst a doctorate dissertation is written to earn a Ph.D.

Do you have a viva after submitting a dissertation or thesis?

You will be required to defend your scholarly work in a viva format as part of your postgraduate studies.

As a masters student you will be required to take part in a dissertation defense; the general idea of this is to ensure you’ve understood your chosen topic and have learnt the skills to perform extensive research on a subject. These usually involve giving a 5 to 10 minute presentation, followed by a round of questions and answers with an internal examiner lasting up to 30 minutes (the exact process may vary depending on the educational institution).

A thesis defense or viva however requires a PhD student to present substantial information and supporting evidence to demonstrate how their research has built on previous work to contribute new information to the subject. For this reason, a viva to earn a doctorate degree can often last several hours.

Do you have to perform a literature review as part of a dissertation or thesis?

Yes you do. The main difference is that a literature review for a master’s thesis may be 1,000 to 2,000 words in length whilst for a doctoral thesis, it will be a standalone chapter of around 10,000 words.




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