Plural of Thesis | Definition & Examples
The plural of thesis is theses, pronounced [thee-seez]. It’s a Greek-derived irregular plural noun that doesn’t follow regular pluralization rules, which add “-s” or “-es” to the end of the singular to form the plural.
All students were required to defend their theses in front of a committee of faculty members.
What is the plural of thesis?
The plural of thesis is theses. Some people think that “thesises” or “thesi” are the plural of “thesis,” but those are incorrect.
- The panel of experts discussed the merits of the competing theses during the debate.
- The university encourages students to publish their theses in academic journals.
- Several of the thesises addressed ethical considerations in modern technology.
- Networking at the conference allowed her to connect with other authors of similar thesi.
What is an irregular plural?
Theses is considered an irregular plural noun. Unlike regular plural nouns (e.g., pizza/pizzas and class/classes), you don’t simply add an “-s” or “-es” to the singular form of an irregular plural noun. This is why the plural of “thesis” is not “thesises,” even though this is a common misspelling.
Thesis is a Greek-derived word and follows Greek pluralization rules, meaning you change the “-is” at the end of the singular form to “-es” to create the plural (e.g., analysis/analyses and axis/axes).
Not all irregular plurals come from Greek origins. Some irregular plurals are Latin-derived words, and others come from other linguistic origins like Old English or Dutch.
| Singular | Plural |
|---|---|
| goose | geese |
| person | people |
| oasis | oases |
| hoof | hooves |
A zero plural is another type of plural noun, which is a noun that remains the same in both the singular and plural forms.
| Singular | Plural |
|---|---|
| shrimp | shrimp |
| deer | deer |
| police | police |
| spacecraft | spacecraft |
Frequently asked questions about the plural of thesis
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Cove, R. (2025, January 14). Plural of Thesis | Definition & Examples. Scribbr. Retrieved March 24, 2025, from https://www.scribbr.com/plurals/plural-of-thesis/
