hypothesis

American  

[hahy-poth-uh-sis, hi-] / haɪˈpɒθ ə sɪs, hɪ- /

noun

plural

hypotheses

1. a proposition, or set of propositions, set forth as an explanation for the occurrence of some specified group of phenomena, either asserted merely as a provisional conjecture to guide investigation working hypothesis or accepted as highly probable in the light of established facts.

2. a proposition assumed as a premise in an argument.

3. the antecedent of a conditional proposition.

4. a mere assumption or guess.

---

hypothesis British  

/ haɪˈpɒθɪsɪs /

noun

1. a suggested explanation for a group of facts or phenomena, either accepted as a basis for further verification ( working hypothesis ) or accepted as likely to be true Compare theory

2. an assumption used in an argument without its being endorsed; a supposition

3. an unproved theory; a conjecture

---

hypothesis Scientific  

/ hī-pŏth′ĭ-sĭs /

plural

hypotheses

1. A statement that explains or makes generalizations about a set of facts or principles, usually forming a basis for possible experiments to confirm its viability.

---

hypothesis Cultural  

1. plur. hypotheses (heye-poth-uh-seez) In science, a statement of a possible explanation for some natural phenomenon. A hypothesis is tested by drawing conclusions from it; if observation and experimentation show a conclusion to be false, the hypothesis must be false. (See scientific method and theory.)

---

Usage

What is a hypothesis? In science, a hypothesis is a statement or proposition that attempts to explain phenomena or facts. Hypotheses are often tested to see if they are accurate. Crafting a useful hypothesis is one of the early steps in the scientific method, which is central to every field of scientific experimentation. A useful scientific hypothesis is based on current, accepted scientific knowledge and is testable. Outside of science, the word hypothesis is often used more loosely to mean a guess or prediction.

Related Words

See theory.

Other Word Forms

• counterhypothesis noun
• hypothesist noun
• subhypothesis noun

Etymology

Origin of hypothesis

First recorded in 1590–1600, hypothesis is from the Greek word hypóthesis “basis, supposition”; hypo-, thesis

Explanation

In science, a hypothesis is an idea or explanation that you then test through study and experimentation. Outside science, a theory or guess can also be called a hypothesis. A hypothesis is something more than a wild guess but less than a well-established theory. In science, a hypothesis needs to go through a lot of testing before it gets labeled a theory. In the non-scientific world, the word is used a lot more loosely. A detective might have a hypothesis about a crime, and a mother might have a hypothesis about who spilled juice on the rug. Anyone who uses the word hypothesis is making a guess.

Example Sentences

As a matter of simple arithmetic, that is far too small a sample to rule out my hypothesis if we take Pangram’s other claims at face value.

From The Wall Street Journal • Apr. 3, 2026

Subject lines include “Recognizing the need for fasting,” “Mice blood age affects Alzheimer’s brain changes,” and “A casual hypothesis about epigenetics.”

From Slate • Mar. 30, 2026

The biggest flaw in the Hegelian viewpoint about supposedly great men is that his entire hypothesis about an unfolding historical process is flat wrong.

From Salon • Mar. 28, 2026

"We were exceptionally lucky to find these -- a real 'needle-in-a-haystack' effort. These prove the impact crater hypothesis beyond doubt, because they have a fabric that can only be created by extreme shock pressures."

From Science Daily • Mar. 11, 2026

Kepler distinguished between a geometrical hypothesis—the mathematical model used to generate predictions—and an astronomical hypothesis, the actual path of the planet through the heavens.

From "The Invention of Science" by David Wootton

Related Words

• assumption
• axiom
• conclusion
• conjecture
• explanation
• guess
• inference
• interpretation
• premise
• proposition
• rationale
• supposition
• theorem
• thesis