A hypothesis is an idea or explanation that you test through study and experimentation; a proposed explanation for an observed phenomenon.
What Does Hypothesis Mean?
Hypothesis comes from Greek hupothesis, meaning "foundation" or "supposition" — literally "a placing under". It entered English in the 16th century through Latin and has been at the heart of scientific and academic language ever since. A hypothesis is not simply a random guess; it is an informed, testable prediction grounded in prior observation.
In academic and scientific writing, a hypothesis is the starting point of an investigation. You propose a hypothesis, design an experiment to test it, then either support or reject it based on the evidence gathered. Common synonyms include theory, conjecture, proposal, and assumption, though each carries a slightly different level of evidence and certainty.
A frequent ESL error is using hypothesis and theory interchangeably. In everyday speech, both can mean "a guess", but in scientific contexts, a theory has already been tested and widely supported, whereas a hypothesis is still awaiting evidence. The plural form — hypotheses — also catches many learners off guard; it follows the Greek pattern (-sis → -ses), just like thesis/theses and analysis/analyses.
Example Sentences
| Sentence | Usage note |
|---|---|
| The researchers proposed a hypothesis that increased screen time disrupts adolescent sleep patterns. | propose a hypothesis — formal academic |
| After months of testing, the data supported their original hypothesis. | support a hypothesis — research context |
| The results failed to confirm the hypothesis, so the team revised their approach. | confirm / reject a hypothesis — scientific report |
| Her hypothesis was that a warmer climate leads to earlier bird migration. | her hypothesis was that — indirect statement |
| We need more evidence before we can move beyond a working hypothesis. | working hypothesis — provisional idea |
| In statistics, you begin by stating the null hypothesis before running any tests. | null hypothesis — technical/statistical use |
| My hypothesis is that people read faster on paper than on screens. | informal academic writing, first person |
| Several competing hypotheses have been put forward to explain the extinction of the dinosaurs. | plural form: hypotheses |
Word Forms
Common Collocations
| Collocation | Example phrase |
|---|---|
| form a hypothesis | "They formed a hypothesis based on preliminary data." |
| test a hypothesis | "The experiment was designed to test the hypothesis." |
| propose / put forward a hypothesis | "The paper proposes a new hypothesis about language acquisition." |
| support / confirm a hypothesis | "The findings strongly supported the hypothesis." |
| reject / disprove a hypothesis | "The results led us to reject the null hypothesis." |
| working hypothesis | "We are operating under a working hypothesis." |
| null hypothesis | "State the null hypothesis before collecting data." |
| alternative hypothesis | "The alternative hypothesis predicts a significant effect." |
Common Mistakes
Watch Out For
The scientists tested several hypothesises.
The scientists tested several hypotheses. (Greek plurals: -sis → -ses)
According to my hypothesis, I think that eating sugar causes hyperactivity.
My hypothesis is that eating sugar causes hyperactivity. (avoid "I think" after "hypothesis" — it is redundant)
The theory of evolution is just a hypothesis.
In science, a theory is stronger than a hypothesis — it has been tested and widely supported. Evolution is a scientific theory, not merely a hypothesis.