Whats the Plural of Hypothesis: Understanding Grammatical Number
Quick Answer
The plural of hypothesis is hypotheses. The word “hypothesises” is not correct in English.
One: She has a new hypothesis about the result.
More than one: The students wrote down their hypotheses before the test.
Hypothesis Becomes Hypotheses — See the Pattern
Look at these words. Can you see what happens?
- one hypothesis → two hypotheses
- one thesis → two theses
- one analysis → two analyses
- one crisis → two crises
Did you see the pattern? The -is at the end changes to -es. This rule works for many English words that come from Greek.
| One (singular) | More than one (plural) |
|---|---|
| hypothesis | hypotheses |
| thesis | theses |
| analysis | analyses |
| crisis | crises |
| basis | bases |
Why It Is Hypotheses and Not Hypothesises
Most English plurals just add -s or -es to the end of the word: cat → cats, box → boxes. But the word hypothesis comes from Greek. Greek words that end in -is follow a special rule. The -is changes to -es:
- hypothesis → hypotheses (not “hypothesises”)
- thesis → theses (not “thesises”)
- analysis → analyses (not “analysises”)
A hypothesis is an idea you want to test. Scientists make a hypothesis before they do an experiment. Students sometimes write a hypothesis at school. You say it like “hi-POTH-eh-sis” for one, and “hi-POTH-eh-seez” for more than one.
Easy way to remember: Think of thesis → theses. They are like sisters. Hypothesis works the same way: hypothesis → hypotheses.
The Rule in One Line: Hypothesis ends in -is, so the plural is hypotheses (-is → -es).
How to Use Hypothesis and Hypotheses in Everyday English
- The teacher asked us to write down our hypothesis before the experiment. (one idea)
- The scientists tested three different hypotheses in the lab. (more than one)
- My hypothesis is that plants grow faster with music. (one idea)
- The team had two hypotheses about why the bridge fell. (more than one)
- His hypothesis was wrong, but he learned a lot from the test. (one idea)
You are doing great. Now let us look at the mistakes most learners make with this word.
The Most Common Mistakes With Hypothesis
Many learners write “hypothesises” because most English plurals just add -s or -es. That is a smart guess — but it does not work for words from Greek. Even advanced learners mix this up sometimes. So if you get confused, you are not alone.
✗ The team tested many hypothesises.
✓ The team tested many hypotheses.
✗ She wrote down her hypothes.
✓ She wrote down her hypothesis.
✗ Both hypothesis were wrong.
✓ Both hypotheses were wrong.
How to remember: The word ends in -is. If you see -is at the end, change it to -es. Hypothesis → hypotheses. Simple.
One small thing to watch: the spelling looks almost the same, but the sound changes. Hypothesis ends with a soft “sis” sound. Hypotheses ends with a “seez” sound, like “bees” or “trees”. If you say “seez” at the end, you are using the plural.
Other words like this: thesis → theses, analysis → analyses, crisis → crises, basis → bases, axis → axes.
Test Yourself: Hypothesis or Hypotheses?
Choose the correct answer for each sentence. Click Check to see if you are right.
1. The students tested three different _______ in the science lab.
2. My _______ is that the plant will grow faster in sunlight.
3. The team wrote down all their _______ before they started the experiment.
4. He had one strong _______ about why the engine stopped working.
5. The book listed five popular _______ about how the universe began.
Keep Going — You Are Building Something
You just learned that hypothesis becomes hypotheses. That is one more plural you will never get wrong again.
But here is something interesting. The word thesis follows the same Greek rule — and university students all over the world write one. Do you know how to talk about two theses? And what is the real difference between a thesis and a hypothesis?
Next lesson: What Is the Plural of Thesis?
Sources
Definition of hypothesis — Cambridge Dictionary
My name is Khamis Maiouf. I am the creator of the English Teacher Site, dedicated to providing valuable resources and insights for students around the world. With a passion for education and a commitment to helping students enhance their skills, I aim to make English teaching more effective and enjoyable for both educators and students.
