Common Mistakes with the Plural of Hypothesis
If you have ever written a research paper, a lab report, or even a thoughtful email about a theory, you have probably needed the plural of hypothesis. The correct plural is hypotheses. This is not a simple case of adding an -s or -es. Because hypothesis comes from Greek, it follows a specific pattern: the singular ending -sis changes to -ses in the plural. Many learners and even native speakers make mistakes here, writing hypothesises, hypothesis (for plural), or hypothesi. This guide will help you use the correct form every time, with clear examples and practical advice for academic writing, emails, and everyday conversation.
Quick Answer: What Is the Plural of Hypothesis?
The plural of hypothesis is hypotheses (pronounced hy-POTH-uh-seez).
- Singular: hypothesis (hy-POTH-uh-sis)
- Plural: hypotheses (hy-POTH-uh-seez)
This change follows the Greek plural rule for words ending in -sis. Other examples include thesis → theses, crisis → crises, and analysis → analyses. Never add a regular English -s or -es to these words.
Why Do People Make Mistakes with the Plural of Hypothesis?
The confusion usually comes from two sources. First, the word looks like it should follow regular English rules. Second, the singular form hypothesis ends in -s, which makes some writers think it is already plural. Here are the most common errors:
Common Mistake 1: Using “Hypothesis” for Both Singular and Plural
Some writers treat hypothesis as an uncountable noun or simply forget to change it. This is incorrect in formal and most informal contexts.
Incorrect: The scientist tested several hypothesis during the experiment.
Correct: The scientist tested several hypotheses during the experiment.
Common Mistake 2: Adding a Regular Plural Ending
Adding -es to make hypothesises is a very common error. This form does not exist in standard English.
Incorrect: We need to evaluate all the hypothesises before the meeting.
Correct: We need to evaluate all the hypotheses before the meeting.
Common Mistake 3: Confusing the Spelling with “Hypothesize”
The verb to hypothesize (or hypothesise in British English) sometimes causes confusion. Remember that hypotheses is a noun (plural), while hypothesizes is a verb (third person singular).
Incorrect: The researcher hypotheses that the results will change.
Correct: The researcher hypothesizes that the results will change.
Comparison Table: Singular vs. Plural of Hypothesis
| Feature | Singular (Hypothesis) | Plural (Hypotheses) |
|---|---|---|
| Number | One | More than one |
| Pronunciation | hy-POTH-uh-sis | hy-POTH-uh-seez |
| Spelling pattern | Ends in -sis | Ends in -ses |
| Example sentence | This hypothesis is worth testing. | These hypotheses are worth testing. |
| Common error | Using it for plural | Writing hypothesises |
Natural Examples of “Hypotheses” in Context
Seeing the word used naturally in different situations helps you remember the correct form. Below are examples from academic writing, professional emails, and everyday conversation.
Academic Writing (Formal)
- The study proposed three hypotheses regarding climate change and migration patterns.
- After reviewing the data, the researchers rejected two of the original hypotheses.
- Each of the hypotheses was tested using a double-blind procedure.
Professional Emails (Semi-Formal)
- Could you please share your hypotheses about the drop in user engagement?
- We will discuss the main hypotheses during tomorrow’s team meeting.
- I have attached a document outlining our working hypotheses for the new project.
Everyday Conversation (Informal)
- “I have a few hypotheses about why the Wi-Fi keeps cutting out.”
- “My friends and I came up with some wild hypotheses about the ending of that movie.”
- “She always has interesting hypotheses about people’s behavior.”
Better Alternatives and When to Use Them
While hypotheses is the correct plural, there are times when a different word might be more appropriate depending on your audience and tone.
When to Use “Hypotheses”
Use hypotheses in any formal or academic context, such as research papers, scientific reports, university assignments, and professional presentations. It is also perfectly fine in semi-formal emails and serious discussions.
Better Alternatives for Informal Contexts
If you are speaking casually or writing to a general audience, you can use simpler terms that carry a similar meaning.
- Theories – Use when the ideas are well-developed. “I have a few theories about why the project failed.”
- Ideas – Use for very informal brainstorming. “Let’s share our ideas about what might happen.”
- Guesses – Use when the ideas are not based on strong evidence. “We made some guesses about the outcome.”
- Assumptions – Use when the ideas are taken for granted. “Our assumptions need to be checked.”
Choosing the right word depends on the level of formality and the strength of the evidence behind the idea. In academic writing, always stick with hypotheses.
Common Mistakes with the Plural of Hypothesis (Detailed)
Let us look at more examples of mistakes and how to fix them.
Mistake: Using “Hypothesis” as a Plural in Formal Writing
Incorrect: The paper presents two main hypothesis that guide the research.
Correct: The paper presents two main hypotheses that guide the research.
Mistake: Adding an Apostrophe
Some writers incorrectly add an apostrophe to make a plural, such as hypothesis’ or hypotheses’. Apostrophes are used for possession, not plurals.
Incorrect: The hypothesis’ were all supported by the data.
Correct: The hypotheses were all supported by the data.
Mistake: Confusing with “Hypothesize” (Verb)
Remember that hypothesize is a verb. The plural noun is hypotheses.
Incorrect: The team hypotheses that sales will increase.
Correct: The team hypothesizes that sales will increase.
Mini Practice: Test Your Knowledge
Choose the correct form to complete each sentence. Answers are below.
- The scientist developed three (hypothesis / hypotheses) for the experiment.
- We need to test this (hypothesis / hypotheses) before moving forward.
- All of the (hypothesis / hypotheses) were presented at the conference.
- She (hypothesis / hypothesizes) that the new drug will be effective.
Answers
- hypotheses (plural, three)
- hypothesis (singular, this)
- hypotheses (plural, all of)
- hypothesizes (verb, third person singular)
FAQ: Common Questions About the Plural of Hypothesis
1. Is “hypotheses” the only correct plural?
Yes. In standard English, the only correct plural of hypothesis is hypotheses. Forms like hypothesises or hypothesi are not accepted in any formal or informal context.
2. How do you pronounce “hypotheses”?
The singular hypothesis is pronounced hy-POTH-uh-sis. The plural hypotheses is pronounced hy-POTH-uh-seez. The last syllable changes from “sis” to “seez.”
3. Can I use “hypothesis” as a plural in informal writing?
It is not recommended. Even in informal writing, using hypothesis for more than one idea will look like a mistake. Stick with hypotheses or use a simpler word like ideas or theories.
4. What are other words that follow the same pattern?
Many Greek-derived words ending in -sis follow this pattern. Common examples include thesis → theses, crisis → crises, analysis → analyses, parenthesis → parentheses, and diagnosis → diagnoses. Learning this pattern will help you with all of them.
Final Tips for Using the Plural of Hypothesis
To avoid mistakes, remember these three points:
- Change -sis to -ses: This is the core rule. One hypothesis, two hypotheses.
- Do not add extra letters: Never write hypothesises or hypothesi.
- Check your verb: If you mean the action of forming an idea, use the verb hypothesize, not the noun hypotheses.
For more help with tricky plural forms, explore our guides on Confusing Plurals and Plural Spelling Rules. If you have questions about this or other topics, feel free to contact us. You can also read our Editorial Policy to learn how we create our content.
