Guide
Dissertation defence (viva)
The dissertation defence — known in the UK as the viva voce — is the oral examination in which a candidate explains and defends their research before expert examiners.
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What the viva is
The viva voce — Latin for "by living voice" — is an oral examination, most associated with doctoral degrees, in which the candidate defends their thesis in conversation with examiners who have read it closely. It serves several purposes at once: to confirm the work is genuinely the candidate’s own, to test their understanding of their field and their methodological choices, to probe the originality and significance of the contribution, and to clarify points the written thesis left open. Far from a hostile interrogation, it is a scholarly examination of whether the work meets the standard for the degree.
Formats vary by country
There is no single model. The classic UK viva is a private, in-depth oral examination conducted by an internal and an external examiner, often lasting a few hours, with no audience. In much of continental Europe and Scandinavia the defence is a public event, sometimes ceremonial, before a committee and an audience. In the United States the dissertation defence is typically held before a committee and may include a public presentation followed by questions. Increasingly, vivas may be held online. Always confirm the format, examiners and expectations for your own institution well in advance.
How to prepare
Re-read your thesis critically, as an examiner would, and be ready to summarise its contribution in a sentence or two. Anticipate likely questions: why this topic, why these methods over alternatives, what the key findings and limitations are, and how the work contributes to knowledge. Know the literature you cite and the debates around it, and prepare honest answers about weaknesses — examiners respect a candidate who can discuss limitations openly. A mock viva with peers or your supervisor is one of the most effective forms of preparation, building both familiarity and confidence.
Possible outcomes
Outcomes vary by institution but commonly fall on a spectrum. The best is a pass with no, or only minor, corrections — small typographical or presentational fixes completed quickly. More often the result is a pass subject to minor or major revisions, where the candidate amends the thesis within a set period before the degree is confirmed; major revisions can require substantial rework and sometimes a re-examination. Rarer outcomes include the award of a lower degree, or, in unusual cases, a fail. A clear pass with minor corrections is the most common result for well-prepared candidates.
Key facts
At a glance
- Definition: an oral examination defending the thesis before expert examiners
- UK term: viva voce ("by living voice"), usually private
- Examiners: typically an internal and an external examiner at doctoral level
- Format note: public defence in much of Europe and the US; private viva in the UK
- Preparation: re-read the thesis, anticipate questions, hold a mock viva
- Outcomes: pass with minor or major corrections; rarely a fail
Common questions
FAQ
What is the difference between a viva and a defence?+
They name the same thing in different traditions. "Viva voce" (or just "viva") is the UK term for the oral examination of a thesis, usually a private examination by internal and external examiners. "Defence" (or "defense") is the term more common in the US and parts of Europe, where it is often a committee examination, sometimes public. Both are the oral defence of the research.
How long does a viva last?+
It varies considerably. A UK doctoral viva commonly runs from one to three hours, sometimes longer, depending on the thesis and the examiners. Public defences elsewhere may include a set presentation followed by questions within a scheduled slot. There is no fixed duration, so ask your institution and supervisor what to expect for your degree.
Can you fail a viva?+
Outright failure is possible but uncommon, especially when the supervisor judged the thesis ready for submission. Far more often the result is a pass requiring minor or major corrections completed within a set period. A candidate may also, in some cases, be offered a lower degree. Thorough preparation and an honest grasp of the work’s limitations make a clear pass much more likely.
