Thesis vs Dissertation: What’s the Difference?
Quick answer: In the UK, a ‘dissertation’ usually refers to the research project for an undergraduate or master’s degree, while a ‘thesis’ refers to the much longer research project for a PhD or doctorate. (Confusingly, in the US the terms are reversed.) The thesis is longer, more original, and defended in a viva.
The UK meaning
In British universities:
- Dissertation — the final research project for a bachelor’s or master’s degree.
- Thesis — the substantial, original research project for a PhD or doctorate.
Key differences
| Dissertation (UK) | Thesis (UK) |
|---|
| Level | Undergraduate / master’s | PhD / doctorate |
| Length | 8,000–20,000 words | 70,000–100,000 words |
| Originality | Applies existing research | Original contribution to knowledge |
| Defence | Usually none | Oral viva voce examination |
Why the confusion?
The terms are reversed in American usage — there a ‘thesis’ is the master’s project and a ‘dissertation’ is the PhD. Always interpret the word by the country and institution.
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Frequently Asked Questions
Is a thesis harder than a dissertation?
A PhD thesis is longer and must make an original contribution to knowledge, so it is generally more demanding than an undergraduate or master’s dissertation.
Do UK and US use these terms the same way?
No — they’re reversed. In the UK a thesis is the PhD; in the US a dissertation is the PhD.
Does a dissertation need original research?
Master’s dissertations often involve some original data, but a PhD thesis must make a genuinely original contribution to the field.
What is a viva?
An oral examination (viva voce) in which PhD candidates defend their thesis to examiners. Dissertations usually don’t require one.
Which is longer?
A PhD thesis (70,000–100,000 words) is far longer than an undergraduate or master’s dissertation.