PhD Thesis vs Dissertation: Key Differences

In the US, a thesis is for a master's degree and a dissertation is for a PhD. In the UK, it's reversed: a dissertation is for undergraduate or master's work, and a thesis is for a PhD. Terms vary by country and university.

If you're pursuing graduate studies, you've likely encountered the terms "thesis" and "dissertation" used interchangeably—and confusingly. The truth is, these terms mean different things depending on where you study. This comprehensive guide clarifies the terminology, explains the requirements for each, and walks you through the entire process from proposal to defense.

Understanding the Definition: What is a Dissertation?

A dissertation is a lengthy, formal document presenting the author's research and findings, submitted in support of candidature for an academic degree. The term comes from the Latin dissertātiō, meaning "discussion"—reflecting its purpose of thoroughly examining and defending a scholarly argument.

In the American academic context, a dissertation:

• Is required for doctoral degrees (PhD, EdD, DBA)
• Represents original research that contributes new knowledge to your field
• Often spans 150-300+ pages depending on the discipline and format
• Must be defended before a committee of experts
• Often takes several years to complete after coursework (varies widely by field and funding)

The dissertation is the capstone of doctoral education—proof that you can independently conduct rigorous research and contribute meaningfully to scholarly discourse.

Understanding the Definition: What is a Thesis?

A thesis comes from the Greek θέσις (thésis), meaning "something put forth" or a proposition. Historically, it referred to an intellectual position taken during academic debate.

In the American context, a thesis:

• Is typically required for master's degrees
• Demonstrates mastery of existing scholarship and analytical ability
• Usually spans 50-100 pages
• May or may not require an oral defense
• Takes 1-2 years to complete

However, the term "thesis" is also used for undergraduate honors projects at selective universities, where students complete substantial research in their senior year.

Thesis vs Dissertation: US vs UK Terminology

The most important thing to understand is that terminology varies by country and sometimes by university. This table clarifies the common conventions:

The American System

In the United States:

• Master's thesis: A research project demonstrating mastery of your field, typically 50-100 pages
• Doctoral dissertation: Original research contributing new knowledge, typically 150-300+ pages
• Senior thesis: An optional honors project for undergraduates at selective colleges

At most U.S. universities, the dissertation is the defining requirement for the doctorate. According to institutional guidelines, a dissertation must make "an original and unique contribution to scholarship."

The British System

In the United Kingdom:

• Undergraduate dissertation: A substantial project (often 8,000-15,000 words) for bachelor's degrees
• Master's dissertation: Required for taught master's degrees (often 15,000-20,000 words)
• Doctoral thesis: The defining work for PhD and research master's degrees (typically 80,000-100,000 words, though limits vary by institution)

The doctoral thesis in the UK is examined through a viva voce ("by live voice"), an oral examination typically lasting 2-3 hours with internal and external examiners.

Other Countries

Key Differences Beyond Terminology

While the terms may swap between regions, there are substantive differences between master's-level and doctoral-level work:

1. Purpose and Scope

2. Length and Depth

Master's level work typically ranges from:

• 50-100 pages (US thesis)
• 15,000-20,000 words (UK dissertation)

Doctoral level work typically ranges from:

• 150-300+ pages (US dissertation, varies widely by field)
• 80,000-100,000 words (UK thesis, though limits vary by institution)

However, length varies dramatically by field:

• Humanities: Longer, more narrative-driven documents
• STEM: Often shorter but with extensive data appendices
• Social Sciences: Middle range with mixed methods

3. Timeline

Based on comprehensive PhD timeline research, here's how these projects typically unfold:

4. Committee and Examination

Master's thesis:

• Typically overseen by 2-3 committee members
• May require oral defense (varies by program)
• Committee provides formative feedback

Doctoral dissertation:

• Often 3-5 committee members; some universities require an external reader
• Oral defense required at virtually all institutions
• Committee serves as examination board

How to Write a Dissertation: Step-by-Step Guide

Whether you're working on a doctoral dissertation or a master's thesis, the process follows similar stages. Here's a comprehensive roadmap:

Stage 1: Choosing Your Topic (2-6 months)

Your topic should be:

1. Personally interesting: You'll spend years on this—passion matters
2. Academically significant: It must contribute to your field
3. Feasible: Achievable within your timeline and resources
4. Original: Not duplicating existing work (for dissertations)

Stage 2: Literature Review (3-6 months)

The literature review:

• Surveys existing research in your area
• Identifies gaps your work will address
• Establishes your theoretical framework
• Demonstrates your expertise to the committee

This isn't just summarizing sources—it's critically analyzing how existing research shapes your project and what remains unknown.

Stage 3: Developing Your Proposal (2-4 months)

Your dissertation proposal typically includes:

1. Introduction: Research questions and significance
2. Literature Review: Context and theoretical framework
3. Methodology: How you'll conduct your research
4. Timeline: Realistic schedule for completion
5. Preliminary Bibliography: Sources you'll engage with

Most programs require a formal proposal defense before you can proceed to research.

Stage 4: Conducting Research (1-3 years)

This is the heart of doctoral work:

• Qualitative research: Interviews, observations, textual analysis
• Quantitative research: Experiments, surveys, statistical analysis
• Mixed methods: Combining approaches for comprehensive insight

Keep detailed records, maintain regular communication with your advisor, and adapt as your research evolves.

Stage 5: Writing the Dissertation (6-18 months)

Most dissertations follow this structure:

Some fields (particularly sciences) use a "three-paper model" where chapters are publishable articles.

Stage 6: Defense Preparation (1-3 months)

Preparing for your defense:

1. Submit your dissertation to committee members 2-4 weeks before defense
2. Create a presentation summarizing your work (typically 20-40 minutes)
3. Anticipate questions: Prepare responses to potential critiques
4. Practice: Do mock defenses with colleagues
5. Know your limitations: Be ready to discuss what you didn't do and why

Stage 7: Final Submission (1-2 months post-defense)

After passing your defense:

1. Make required revisions: Address committee feedback
2. Format according to guidelines: Your institution has specific requirements
3. Submit to graduate school: Usually through ProQuest or similar system
4. Complete administrative requirements: Embargo decisions, copyright registration

Most universities require final submission within 60 days of defense.

The Defense: What to Expect

The dissertation defense (US) or viva voce (UK) is the culminating examination of your doctoral journey.

US Dissertation Defense

Format: Typically 1-2 hours

• 20-40 minute presentation by the candidate
• 1-2 hours of questions from committee
• Often open to the public (audience cannot ask questions)
• Committee deliberates privately, then announces result

Possible outcomes:

• Pass with no revisions (rare)
• Pass with minor revisions (most common)
• Pass with major revisions (requires additional work)
• Fail (extremely rare)

UK Viva Voce

Format: Typically 2-3 hours, no time limit

• No presentation; begins with examiner questions
• Usually private (candidate and examiners only)
• Chair may observe but doesn't ask questions
• More intensive questioning than US model

Possible outcomes:

• Pass with no corrections
• Pass with minor corrections (within 3 months)
• Pass with major corrections (may require re-submission)
• Award MPhil instead of PhD (rare)
• Fail (very rare)

Common Questions About Thesis and Dissertation Writing

How long should a dissertation be?

Length varies by discipline and institution, but typical ranges are:

• Humanities: 70,000-100,000 words (200-300+ pages)
• Social Sciences: 50,000-80,000 words (150-200 pages)
• Sciences: 30,000-60,000 words (80-150 pages, plus appendices)

Quality matters more than quantity. A focused 150-page dissertation can be more valuable than a bloated 400-page document.

Can I publish my dissertation?

Yes, and many scholars do:

• Journal articles: Extract chapters as standalone papers
• Book publication: Revise dissertation into academic book (common in humanities)
• Open access: Many institutions require digital repository submission

Check your institution's embargo policies if you plan to publish.

How do I choose a dissertation committee?

Select members who:

1. Have expertise relevant to your topic
2. Are supportive and responsive
3. Complement each other (methodological diversity helps)
4. Have reasonable availability
5. Work well together

Your advisor's input is crucial—they know the political dynamics of your department.

What if I'm struggling with my dissertation?

This is normal. Strategies include:

• Write regularly: Even 30 minutes daily builds momentum
• Set micro-goals: "Finish one paragraph" not "write chapter 3"
• Join writing groups: Accountability helps
• Seek support: Use your institution's writing center
• Talk to your advisor: They've seen this before

Dissertation completion rates improve with structure, support, and realistic expectations.

Related Resources

Understanding the thesis and dissertation is essential for anyone pursuing advanced degrees. Explore these related guides for deeper context:

• How Long Does It Take to Get a PhD? - Comprehensive timeline guide
• What is a PhD? - Understanding doctoral degrees
• Can You Get a PhD Online? - Online doctoral program guide

Browse more content on PhD, Grad School, and Research.

Conclusion

The thesis vs dissertation distinction ultimately comes down to geography and degree level. What matters most is understanding the requirements of your specific program and executing high-quality scholarly work.

Whether you're writing a master's thesis in the US, a doctoral thesis in the UK, or a dissertation anywhere in the world, the core challenge is the same: conducting rigorous research, presenting it clearly, and defending your conclusions before experts.

Start early, stay organized, seek support when needed, and remember that millions of scholars have successfully navigated this path before you. Your contribution to knowledge awaits.

Amos Oppong is an entrepreneur leveraging AI applications to solve everyday problems. He is the brain behind Streamlined AI, a platform connecting students with academic advisors worldwide.