What Is the Plural of Hypothesis?
The plural of hypothesis is hypotheses. This follows the standard rule for many English words that end in -is, where the ending changes to -es in the plural. You will never use “hypothesises” or “hypothesi” in standard academic or everyday English. The word hypothesis comes from Greek, and its plural form hypotheses preserves that original pattern.
Quick Answer
Singular: hypothesis
Plural: hypotheses
Pronunciation: Singular: /haɪˈpɒθəsɪs/ (hy-POTH-uh-sis); Plural: /haɪˈpɒθəsiːz/ (hy-POTH-uh-seez)
Use hypotheses when you are talking about more than one proposed explanation or assumption. This is true whether you are writing a research paper, sending a professional email, or having a casual conversation about science.
Why the Plural Is “Hypotheses”
The word hypothesis is a noun of Greek origin that entered English through Latin. In Greek, many nouns ending in -sis form their plural by changing the ending to -ses. English has kept this pattern for a set of academic and scientific terms. Other common examples include thesis (plural theses), crisis (plural crises), and analysis (plural analyses).
Because this is a fixed rule, you do not add a regular English -s or -es ending. Writing “hypothesises” is a common error, but it is always incorrect in standard English. The same applies to “hypothesi,” which is not a word at all.
Formal vs. Informal Use
Formal Contexts (Academic Writing, Research, Professional Reports)
In formal writing, hypothesis and hypotheses are used with precision. You will often see them in scientific papers, grant proposals, and academic discussions. The tone is objective and careful.
Example (formal): “The researcher tested three hypotheses during the experiment.”
Example (formal): “Our initial hypothesis was not supported by the data.”
Informal Contexts (Conversation, Emails, Everyday Discussion)
In everyday conversation, people still use hypothesis and hypotheses correctly, but the surrounding language is less strict. You might hear someone say, “I have a hypothesis about why the Wi-Fi is slow,” even if they are not a scientist. The plural is less common in casual talk, but it appears when someone is discussing multiple ideas.
Example (informal): “We came up with a few hypotheses for why the project was delayed.”
Example (informal email): “Let me share my hypothesis about the client’s feedback.”
Comparison Table: Hypothesis vs. Hypotheses
| Feature | Hypothesis (Singular) | Hypotheses (Plural) |
|---|---|---|
| Number | One | More than one |
| Pronunciation | /haɪˈpɒθəsɪs/ | /haɪˈpɒθəsiːz/ |
| Common in | Science, research, everyday reasoning | Research papers, data analysis, group discussions |
| Verb agreement | “The hypothesis is…” | “The hypotheses are…” |
| Example | This hypothesis explains the results. | These hypotheses need further testing. |
Natural Examples
Here are examples that show how hypothesis and hypotheses appear in real writing and speech.
- Research paper: “The study tested two competing hypotheses about memory retention.”
- Classroom discussion: “Can anyone offer a hypothesis for why the experiment failed?”
- Business meeting: “We have several hypotheses about the drop in sales, but we need more data.”
- Everyday conversation: “My hypothesis is that the traffic is worse because of the construction.”
- Email to a colleague: “I have a hypothesis about the software bug. Let me explain.”
Common Mistakes
Even advanced English learners sometimes make errors with this word. Here are the most frequent mistakes and how to avoid them.
Mistake 1: Using “Hypothesises”
Incorrect: “The scientist proposed several hypothesises.”
Correct: “The scientist proposed several hypotheses.”
Why: The plural of hypothesis is not formed by adding -es. It changes the -is ending to -es.
Mistake 2: Using “Hypothesi”
Incorrect: “We need to test both hypothesi.”
Correct: “We need to test both hypotheses.”
Why: “Hypothesi” is not a word in English. The plural form must end in -es.
Mistake 3: Confusing Singular and Plural in Verb Agreement
Incorrect: “The hypotheses is supported by the evidence.”
Correct: “The hypotheses are supported by the evidence.”
Why: Hypotheses is plural, so it requires a plural verb.
Mistake 4: Using “Hypothesis” as a Plural
Incorrect: “We have three hypothesis to consider.”
Correct: “We have three hypotheses to consider.”
Why: The singular form cannot be used for more than one item.
Better Alternatives and When to Use Them
In some contexts, you might choose a different word instead of hypothesis or hypotheses to match the tone or clarity you need. Here are a few alternatives.
- Assumption: Use when the idea is taken for granted without proof. Example: “Our assumption was that the system would work.”
- Theory: Use for a well-tested and widely accepted explanation. Example: “The theory of evolution is supported by decades of research.”
- Guess: Use in very informal contexts when the idea is not based on strong evidence. Example: “That is just a guess.”
- Proposition: Use in formal or logical discussions. Example: “The proposition requires further analysis.”
- Idea: Use in everyday conversation for a general thought. Example: “I have an idea about how to fix this.”
Choose hypothesis or hypotheses when you want to sound precise and scientific. Use the alternatives when you need a more casual or general word.
Mini Practice: Test Your Knowledge
Choose the correct word to complete each sentence. Answers are below.
- The researcher developed a new __________ to explain the phenomenon.
a) hypothesis
b) hypotheses - Several __________ were proposed during the meeting.
a) hypothesis
b) hypotheses - These __________ need to be tested before we can draw conclusions.
a) hypothesis
b) hypotheses - My __________ is that the weather caused the delay.
a) hypothesis
b) hypotheses
Answers
- a) hypothesis (singular, one idea)
- b) hypotheses (plural, more than one)
- b) hypotheses (plural, “these” indicates more than one)
- a) hypothesis (singular, “my” indicates one)
Frequently Asked Questions
1. Is “hypotheses” the only correct plural?
Yes. In standard English, the only correct plural of hypothesis is hypotheses. There are no alternative forms.
2. How do you pronounce “hypotheses”?
The plural hypotheses is pronounced /haɪˈpɒθəsiːz/. The last syllable sounds like “sees” or “seeze.” The singular hypothesis ends with a softer “sis” sound.
3. Can I use “hypothesis” for multiple ideas in informal speech?
No. Even in informal speech, you should use hypotheses for more than one idea. Using the singular form for multiple items will sound incorrect to native speakers.
4. What other words follow the same pattern?
Many words ending in -is change to -es in the plural. Common examples include thesis (theses), crisis (crises), analysis (analyses), diagnosis (diagnoses), and parenthesis (parentheses).
For more help with similar words, visit our Common Plural Forms section. If you have questions about other tricky plurals, check our Confusing Plurals guide. You can also read our FAQ for general questions about plural forms.
