An idea that is suggested as a possible explanation and then tested.
ExampleThe professor explains why the original hypothesis failed.
ExampleThe reading passage presents a hypothesis about the cause of the population decline.
Usage Scenarios
Reading a research passage
Expect a hypothesis to be paired with evidence, especially in biology, archaeology, psychology, and environmental science passages.
ExampleThe fossil record supports the hypothesis that the species migrated during a cooler period.
Listening to a lecture
Notice whether the professor accepts, questions, or replaces the hypothesis as new information appears.
ExampleThe professor mentions recent satellite data to challenge an earlier hypothesis about cloud formation.
Usage Guide
A hypothesis is a possible explanation, not a proven conclusion. TOEFL reading passages often introduce a problem, give one or more hypotheses, and then evaluate the evidence. When you see this word, expect the passage to move between idea and proof.
In lectures, a professor may describe a hypothesis and then add findings that support, weaken, or revise it. That structure matters for listening questions because the test may ask why the professor mentions a detail. The detail often functions as evidence for or against the hypothesis.
Use hypothesis with verbs such as form, propose, test, support, challenge, reject, and revise. These verb partners show that the idea is still being examined. If the answer choice treats the hypothesis as a final fact, be careful.
Word Forms & Word Building
Hypothesis comes from Greek roots: hypo- means under, and thesis means placing or proposition. The word-building idea is useful: a hypothesis is a proposition placed under investigation, not a final truth.
Hypothesis is the noun. The plural is hypotheses, pronounced differently at the end. TOEFL passages may use both forms if several explanations are compared.
Hypothesize is the verb: researchers hypothesize that a chemical signal affects migration. It is more formal than guess because it implies a reasoned explanation that can be tested.
Hypothetical is the adjective. It means imagined, possible, or used for discussion, not confirmed. A hypothetical example can help explain an idea, but it is not evidence by itself.
Meaning Boundaries
Hypothesis vs theory
A hypothesis is a proposed explanation that still needs testing. A theory, especially in academic science, is broader and more established. TOEFL passages may test this difference when they discuss evidence.
Hypothesis vs assumption
An assumption is something accepted without proof, often as a starting point. A hypothesis is more active: it is framed so evidence can test it.
Register
Hypothesis belongs to academic, scientific, and research contexts. In everyday conversation, guess, idea, or explanation may sound more natural.
Best contexts
Use hypothesis in research chains: propose, test, support, challenge, revise, or reject a hypothesis. Avoid it when the sentence only means opinion.
Memory Tricks
Remember hypo- as under: the idea sits under the evidence until the research supports it. That keeps you from treating hypothesis as proven fact.
Use a note-taking mark: write H? beside a proposed explanation, then add plus signs for supporting evidence and minus signs for opposing evidence.
Study it as a research chain: form a hypothesis -> test a hypothesis -> support or reject a hypothesis. That chain matches how TOEFL passages often organize information.
Common Traps
Do not treat hypothesis and theory as identical. In everyday speech they can overlap, but academic passages often use them differently.
Be careful with the plural: hypothesis becomes hypotheses. In TOEFL reading, this plural often appears when a passage compares several possible explanations.
Do not write a hypothesis as if it were already proven. Strong partners are test, support, challenge, reject, and revise because they keep the word in a research frame.