[ hahy-poth-uh-sis, hi- ]
/ haɪˈpɒθ ə sɪs, hɪ- /
Save This Word!
See synonyms for: hypothesis / hypotheses on Thesaurus.com

noun, plural hy·poth·e·ses [hahy-poth-uh-seez, hi-]. /haɪˈpɒθ əˌsiz, hɪ-/.
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.
a proposition assumed as a premise in an argument.
the antecedent of a conditional proposition.
a mere assumption or guess.
There are grammar debates that never die; and the ones highlighted in the questions in this quiz are sure to rile everyone up once again. Do you know how to answer the questions that cause some of the greatest grammar debates?
Question 1 of 7
Which sentence is correct?

Origin of hypothesis

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

synonym study for hypothesis

1. See theory.


hy·poth·e·sist, nouncoun·ter·hy·poth·e·sis, noun, plural coun·ter·hy·poth·e·ses.sub·hy·poth·e·sis, noun, plural sub·hy·poth·e·ses.


1. hypothesis , law, theory (see synonym study at theory)2. deduction, extrapolation, induction, generalization, hypothesis
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023


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.

Why is hypothesis important?

The first records of the term hypothesis come from around 1590. It comes from the Greek term hypóthesis, meaning “basis, supposition.”

Trustworthy science involves experiments and tests. In order to have an experiment, you need to test something. In science, that something is called a hypothesis. It is important to remember that, in science, a verified hypothesis is not actually confirmed to be an absolute truth. Instead, it is accepted to be accurate according to modern knowledge. Science always allows for the possibility that new information could disprove a widely accepted hypothesis.

Related to this, scientists will usually only propose a new hypothesis when new information is discovered because there is no reason to test something that is already accepted as scientifically accurate.

Did you know … ?

It can take a long time and even the discovery of new technology to confirm that a hypothesis is accurate. Physicist Albert Einstein’s 1916 theory of relativity contained hypotheses about space and time that have only been confirmed recently, thanks to modern technology!

What are real-life examples of hypothesis?

While in science, hypothesis has a narrow meaning, in general use its meaning is broader.


Quiz yourself!

True or False?

In science, a hypothesis must be based on current scientific information and be testable.

How to use hypothesis in a sentence

British Dictionary definitions for hypothesis

/ (haɪˈpɒθɪsɪs) /

noun plural -ses (-ˌsiːz)
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 trueCompare theory (def. 5)
an assumption used in an argument without its being endorsed; a supposition
an unproved theory; a conjecture

Derived forms of hypothesis

hypothesist, noun

Word Origin for hypothesis

C16: from Greek, from hupotithenai to propose, suppose, literally: put under; see hypo-, thesis
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for hypothesis

[ hī-pŏthĭ-sĭs ]

Plural hypotheses (hī-pŏthĭ-sēz′)
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.


The words hypothesis, law, and theory refer to different kinds of statements, or sets of statements, that scientists make about natural phenomena. A hypothesis is a proposition that attempts to explain a set of facts in a unified way. It generally forms the basis of experiments designed to establish its plausibility. Simplicity, elegance, and consistency with previously established hypotheses or laws are also major factors in determining the acceptance of a hypothesis. Though a hypothesis can never be proven true (in fact, hypotheses generally leave some facts unexplained), it can sometimes be verified beyond reasonable doubt in the context of a particular theoretical approach. A scientific law is a hypothesis that is assumed to be universally true. A law has good predictive power, allowing a scientist (or engineer) to model a physical system and predict what will happen under various conditions. New hypotheses inconsistent with well-established laws are generally rejected, barring major changes to the approach. An example is the law of conservation of energy, which was firmly established but had to be qualified with the revolutionary advent of quantum mechanics and the uncertainty principle. A theory is a set of statements, including laws and hypotheses, that explains a group of observations or phenomena in terms of those laws and hypotheses. A theory thus accounts for a wider variety of events than a law does. Broad acceptance of a theory comes when it has been tested repeatedly on new data and been used to make accurate predictions. Although a theory generally contains hypotheses that are still open to revision, sometimes it is hard to know where the hypothesis ends and the law or theory begins. Albert Einstein's theory of relativity, for example, consists of statements that were originally considered to be hypotheses (and daring at that). But all the hypotheses of relativity have now achieved the authority of scientific laws, and Einstein's theory has supplanted Newton's laws of motion. In some cases, such as the germ theory of infectious disease, a theory becomes so completely accepted, it stops being referred to as a theory.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for hypothesis

[ (heye-poth-uh-sis) ]

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.)

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.