What is a thesis?
Quick answer
A thesis has two common meanings. A thesis statement is the one- or two-sentence main argument of an essay, usually at the end of the introduction. A thesis can also be a long research paper written to earn a degree, especially a master’s degree.
The word comes from Greek thesis, meaning “a proposition” or “something put forward.” In both meanings, a thesis is a claim you set out to support.
What a thesis statement does
A good thesis statement tells the reader what you’re arguing and often why. Everything else in the essay should support it.
| Weak | Strong |
|---|---|
| Social media is bad. | Social media harms teenagers’ sleep because late-night scrolling delays bedtime and the blue light from screens disrupts melatonin. |
| This essay is about recycling. | Cities should charge for household trash by weight, because pay-as-you-throw programs cut waste and increase recycling. |
| Shakespeare was a great writer. | In Macbeth, Shakespeare uses blood imagery to show how guilt destroys Lady Macbeth more completely than her husband. |
A checklist for a strong thesis
- It makes a claim someone could disagree with, not just a fact.
- It’s specific, naming exactly what you’ll argue.
- It fits the length of the essay.
- It appears near the end of the introduction.
For help with the paragraph around it, see how to write a good essay introduction.
Thesis vs dissertation
| Thesis | Dissertation | |
|---|---|---|
| Usual level (US) | Master’s degree | Doctoral (PhD) degree |
| Purpose | Shows mastery of existing research | Adds new, original research |
| Length | Often 40–100 pages | Often 100–300+ pages |
In the UK and some other countries, the terms are used the other way around, so check your university’s guidelines.
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