The Plural of Thesis: Getting it Right
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The plural of thesis is theses (pronounced THEE-seez).
You use theses when referring to more than one thesis paper or document.
Why is There Confusion Over The Plural of Thesis?
It is a mistake to write the plural of thesis as thesises or thesisi. These are not correct. People make this mistake because they are not used to irregular pluralization.
Is Thesis a Countable or Uncountable Noun?
Thesis can refer to either a research paper (which you can count) or an idea in that paper (which you can’t count). This makes thesis either countable or uncountable depending on context. But the rule’s pretty clear.
When is Thesis Countable?
“Thesis” means a long research paper turned in for a degree. Here, thesis refers to one single paper, so you can use it to talk about multiple projects.
“Thesis” also means the main idea in a long paper. You can’t count ideas, so here thesis is singular.
Where did Thesis Come From?
The word thesis comes from the Greek word θέσις (thesis) meaning “a proposition” or “position.”
In Latin and Greek long ago, thesis meant an argument or proposal. Folks used it for written work or the concept inside it.
The irregular pluralization of thesis comes from its Greek roots.
When Do You Use Theses?
Since a thesis can mean a research paper, it can be plural. When mentioning more than one paper, dissertation or project, use theses.
For example:
- The library collected remarkable theses from last semester.
- The students bound their theses with plastic covers.
When is Thesis Singular?
When thesis refers to just the concept, theory, or proposition in a paper, it’s a single abstract idea. Keep it singular here even with multiple papers.
For instance:
- Her thesis brought insightful ideas to the topic.
- Each thesis offered unique evidence.
Other irregular plurals:
The Bottom Line: The plural of thesis
To sum up, theses is the plural form of thesis when referring to multiple discrete written works. However, thesis itself remains uncountable when used as an umbrella term for an abstract idea. Use theses when mentioning multiple research papers or dissertations. Stick with thesis when discussing the main idea — even for many projects.
Check if thesis refers to:
- One or more physical paper(s) (theses)
- A concept inside one or more paper(s) (thesis)
This basic test makes plurals a piece of cake!
Quick Reference Guide
Thesis:
- Noun referring to a dissertation, treatise or other written work submitted in completion of a degree.
- Countable when referring to multiple discrete works.
Theses:
- Plural form of thesis, used when quantifying multiple treatises or dissertations
