Have you ever come across the word “thesis” and wondered how to make it plural? Maybe you’re writing an essay, studying at university, or just curious about English grammar. At first glance, “thesis” looks like one of those tricky words that don’t follow the usual “add -s” rule. And you’re right it’s a bit special.
In this guide, we’ll explore the plural form of “thesis” in a simple, step-by-step way. We’ll look at what the word means, where it comes from, and most importantly, how to use both its singular and plural forms in everyday sentences. By the end, you’ll feel confident using “thesis” in any context.
So, grab your curiosity, and let’s dive in!
How to Pronounce the Plural (Pronunciation Guide)
Spelling theses correctly is one thing — saying it out loud is another. The singular thesis is pronounced THEE-sis (IPA: /ˈθiːsɪs/), with the stress firmly on the first syllable.
The plural theses is pronounced THEE-seez (IPA: /ˈθiːsiːz/). Notice the final s sound turns into a long z sound, rhyming with “seas” — exactly like analyses (uh-NAL-uh-seez) and diagnoses (dye-AG-no-seez). All these Greek-origin words share the same musical ending.
A handy practice tip: say the trio slowly — THEE-sis, THEE-seez — exaggerating the final sound at first, then speeding up until it feels natural. Saying “several theses” correctly in a classroom or meeting instantly signals that you know the correct plural form.
id=”Frequently_Asked_Questions”>Frequently Asked Questions
Quick answers to the questions learners ask most about the plural of thesis:
What is the plural of thesis?
The plural of thesis is theses. The -is ending changes to -es — the standard Greek plural pattern that English kept. There is no other correct plural form.
How do you pronounce the plural of thesis?
The singular thesis is said THEE-sis (IPA: /ˈθiːsɪs/). The plural theses is said THEE-seez (IPA: /ˈθiːsiːz/), rhyming with “seas.” Only the final sound changes — the stress stays on the first syllable in both.
Why isn’t the plural “thesises”? (Why is it irregular?)
Because thesis comes from Greek, where nouns ending in -is form the plural in -es. English borrowed the word together with its plural rule — the same rule behind analyses, crises, and diagnoses. Adding a regular “-s” ending to an irregular plural is one of the most common mistakes in English.
Do I say “the theses is” or “the theses are”?
Always “the theses are.” Theses is plural, so it takes a plural verb. Compare: “Her thesis is nearly finished” (singular) with “Their theses are nearly finished” (plural).
What Does “Thesis” Mean?
Before we talk about plurals, let’s make sure we’re clear on the meaning of the word itself.
A thesis is:
- A long piece of writing that a student writes to earn a degree (often at the master’s or PhD level).
- A statement or main idea that someone puts forward and then supports with arguments or evidence.
Simple Examples:
- She spent three years writing her thesis on climate change.
- His main thesis is that technology has changed the way we communicate.
So, a thesis can either be an academic paper or a central idea. Now that we know what it means, let’s move to the plural.
What Is the Plural of “Thesis”?
Here’s the straightforward answer:
The correct plural form of “thesis” is “theses.”
Instead of adding “-s” like we do with most nouns, “thesis” joins the family of irregular plurals and changes its ending: the “-is” becomes “-es” — the classic -is to -es rule.
Example Sentences:
- The library has copies of many doctoral theses.
- Different scholars put forward different theses about the origin of language.
So, when you’re talking about more than one thesis, remember to use “theses.”
Why Isn’t It Just “Thesises”?
Great question! English loves to borrow words of Greek origin, and “thesis” is one of them. It comes from Greek, where the plural naturally changes from “-is” to “-es.”
In ancient Greek:
- Singular: thesis
- Plural: theses
English kept that original Greek formation — the same pattern survives in modern plurals. That’s why we don’t say “thesises.”
Other Words That Follow the Same Rule
“Thesis” isn’t alone. Other English words borrowed from Greek or Latin follow the same “-is” to “-es” rule.
Here are a few examples:
- Crisis → Crises
- Analysis → Analyses
- Basis → Bases
- Parenthesis → Parentheses
This pattern makes them feel like part of the same family. If you know one, you can usually guess the others.
Is “Theses” Singular or Plural?
This singular vs plural mix-up is a common point of confusion. The word “theses” is always plural.
- Correct: The professor reviewed three theses today.
- Incorrect: She is writing a theses on psychology.
If you’re talking about just one, use thesis. If you’re talking about more than one, use theses.
Using “Thesis” and “Theses” in Real Life
Let’s look at both forms in action with some example sentences.
Singular (Thesis):
- My thesis argues that social media influences voting behavior.
- He defended his thesis in front of a committee.
Plural (Theses):
- Several theses were submitted to the university this year.
- Philosophers often debate competing theses on human freedom.
See the difference? Usage in sentences makes it clear whether you’re talking about one or many.
How to Remember the Plural Easily
If you find it hard to remember, here’s a quick memory trick:
Think of analysis → analyses. You probably know that one already. Just apply the same rule to “thesis.”
- One analysis → two analyses
- One thesis → two theses
This little mnemonic can save you from second-guessing yourself.
Fun Facts About “Thesis”
Here are a few extra bits to make learning more enjoyable:
- Word Origin: “Thesis” comes from the Greek word tithenai, which means “to put” or “to place.” That makes sense because a thesis is something you “put forward.”
- In Music: In classical music, “thesis” once meant the “downbeat,” or the stronger part of a musical rhythm.
- In Philosophy: Philosophers often use “thesis” to mean a claim or position, especially in debates.
- Famous Example: Martin Luther famously nailed his 95 Theses to a church door in 1517, sparking the Protestant Reformation. Notice the plural here 95 ideas or arguments, not just one!
Common Mistakes Learners Make
Let’s clear up a few common mistakes that often happen:
- Using “thesises”
- Wrong: I have written two thesises.
- Right: I have written two theses.
- Mixing up thesis with theme — two confusable words
- A thesis is a statement or big idea, while a theme is a subject or topic.
- Example: Her thesis is that friendship is the key to happiness. The theme of her story is friendship.
- Forgetting “theses” is plural
- Wrong: He submitted a theses.
- Right: He submitted a thesis.
Why Knowing This Matters
At first, it might feel like a tiny detail. But in academic or professional settings, using the correct plural shows precision and care. Professors, editors, and readers notice these small things. Getting it right can make your writing clearer and more polished.
Plus, it helps you better understand similar words with Greek or Latin origins. Once you master “thesis → theses,” you’ll feel more confident with words like “analysis” or “crisis.”
Quick Recap
Let’s summarize everything we’ve learned so far:
- Thesis (singular): one academic paper or main idea.
- Theses (plural): more than one thesis.
- The change from “-is” to “-es” comes from Greek, and theses is the only dictionary-recognized plural.
- Other words that follow the same rule include “analysis → analyses” and “crisis → crises.”
- Always use “thesis” for one, “theses” for many.
Practice Time
Let’s make sure you’ve got it. Try filling in the blanks with the correct form:
- She is almost finished writing her _______.
- The library has dozens of student _______.
- His main _______ is that education should be free for all.
- Different scientists put forward different _______ about climate change.
Answers:
- thesis
- theses
- thesis
- theses
See? Once you practice, it becomes second nature.
Conclusion
The plural of “thesis” doesn’t have to be confusing. It’s simply “theses.” This unusual form comes from Greek, and it’s the same rule that changes “analysis” into “analyses.”
Remember: one thesis, many theses. That’s it! With a little practice, you’ll use it without hesitation.
So, the next time you’re writing about research papers, ideas, or even Martin Luther’s 95 Theses, you’ll know exactly which form to use. English can be quirky, but once you learn the patterns, it becomes much easier and sometimes even fun.
Now, go ahead and impress your friends, classmates, or teachers by using “thesis” and “theses” with confidence!
