Skip to content

What’s the Plural of Hypothesis?

Last Updated

The plural of “hypothesis”

👍🏼Usage Note

The scientist proposed one hypothesis to explain the observed phenomenon.

The research team developed several testable hypotheses before starting the experiment.

The students formulated three hypothesis for their project.

We discussed various hypothesiss in the meeting.
  • Hypothesis is singular (sounds like hi-paw-thuh-sis).
  • Hypotheses‘ is the plural of hypothesis.

What’s the meaning of hypothesis?

Hypothesis comes from the Greek word, meaning “base, groundwork, foundation”. Hypothesis is made up of the Greek root words, hypo + thesis: “hypo” meaning “under” or “placing under”; “thesis“, meaning “a placing, proposition” (from Etymonline).

So, based on the noun’s construction, hypothesis means to put or set forward a thesis or proposal to be subject to further investigation. According to Wikipedia, hypotheses are:

Tentative conjectures explaining an observation, phenomenon or scientific problem that can be tested by further observation, investigation and/or experimentation.

Wikipedia on the word hypothesis.

Why is “hypotheses” plural for “hypothesis”?

Many people confuse the plural of hypothesis, and it’s not tough to see why: hypothesis is an irregular plural noun form that omits the -s/-es of regular plural nouns. Apart from this, the way hypothesis modifies from singular to plural effectively changes the spelling and pronunciation of the word by substituting the -sis as a singular with –ses as a plural.

Most nouns add an -s/-es to denote plural. Hypothesis, and similar sounding nouns such as crisis, thesis, oasis, nemesis, diagnosis, analysis and so on, all change to -ses in their plural forms.

Nouns that end in “sis”

singular plural
crisis crises
diagnosis diagnoses
hypothesis hypotheses
oasis oases
synopsis synopses
thesis theses

The plural of ‘hypothesis’ by linking it to other -sis words (like thesis, analysis) that change to -ses.

Hypothesis/hypotheses in sentences

Sentences with “hypothesis” singular Sentences with “hypotheses” plural
Other chemists rejected his hypothesis.

What we need is a general hypothesis to explain merger waves.

Their hypothesis is that watching excessive amounts of television reduces a person’s ability to concentrate.

The results of the experiment did not support his hypothesis.

In the above work, we combine the redaction and source hypotheses.

Various hypotheses have been put forward to explain this increase.

Such hypotheses attend to Aristotle’s philosophy at the neglect of his life.

The hypotheses that carried it back to the early years of the Christian era have been wholly abandoned.

Synonyms of “hypothesis”

  • assumption
  • supposition
  • proposition
  • guess
  • conjecture
  • explanation
  • premise
  • inference
  • conclusion
  • interpretation
  • thesis
  • theory
  • supposition
  • proposal

Learn about other nouns!

Origin of “hypothesis”

From etymonline:

1590s, “a particular statement;” 1650s, “a proposition, assumed and taken for granted, used as a premise,” from French hypothese and directly from Late Latin hypothesis, from Greek hypothesis.

Worksheet

Question 1 of 10

According to the blog post, what is the correct plural form of “hypothesis”?



Which of these is a common INCORRECT plural form of “hypothesis” mentioned in the post?



The blog post explains that the plural of “hypothesis” is formed by changing the ending -sis to what?



Based on the post, which of the following words forms its plural in a similar way to “hypothesis”?



According to the blog post, “Hypothesis” (singular) comes from Greek words meaning “under” and “a placing, proposition”. It refers to a tentative conjecture. What is the singular form of this word?



The scientist proposed one to explain the observed phenomenon.



The research team developed several testable before starting the experiment.



The students formulated three for their project.



The blog post notes that many nouns ending in “-sis” in the singular, like hypothesis, change to “-” in their plural forms.



The results of the experiment did not support his .





FAQs

What is the plural of hypothesis?
+

The plural of “hypothesis” is “hypotheses”. This irregular form changes the ending from “-sis” to “-ses”, which is common for Greek nouns like “crisis” becoming “crises”.

How do you spell hypothesis plural?
+

The correct spelling for the plural is “hypotheses”. The singular form ends in “-sis”, while the plural form changes this ending to “-ses” as shown in words like “analysis/analyses”.

Is hypothesis singular or plural?
+

“Hypothesis” is the singular form of the word. The plural form is “hypotheses”. Use “hypothesis” when referring to one, and “hypotheses” for more than one.

Why is hypothesis plural irregular?
+

“Hypothesis” has an irregular plural form because it comes from Greek. Many nouns from Greek ending in “-sis” form their plural by changing the ending to “-ses” instead of adding “-s”.

What is a common hypothesis mistake?
+

A common mistake is using “hypothesis” or “hypothesiss” for the plural form. The correct plural is “hypotheses”. For example, the post notes it’s incorrect to say “three hypothesis”.

Yash, D. "What’s the Plural of Hypothesis?." Grammarflex, Jun 24, 2025, https://www.grammarflex.com/whats-the-plural-of-hypothesis/.

Sources

  1. Wikipedia hypothesis. Synonyms for hypothesis. ‘Hypotheses‘ sentence examples. Origin of ‘hypothesis‘.

The latest from the Grammarflex blog

From grammar and writing to style and clarity, our experts tackle the biggest questions in English and content creation.