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.

Definitions of hypothesis

n a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena

“a scientific hypothesis that survives experimental testing becomes a scientific theory”
possibility, theory
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a hypothetical possibility, circumstance, statement, proposal, situation, etc.
the physically discrete element that Darwin proposed as responsible for heredity
framework, model, theoretical account
a hypothetical description of a complex entity or process
conjecture, speculation
a hypothesis that has been formed by speculating or conjecturing (usually with little hard evidence)
assumption, supposal, supposition
a hypothesis that is taken for granted
a theory that social and cultural events are determined by history
computer simulation, simulation
(computer science) the technique of representing the real world by a computer program
an intuitive assumption
base, basis, cornerstone, foundation, fundament, groundwork
the fundamental assumptions from which something is begun or developed or calculated or explained
mean sun
a theoretical sun that moves along the celestial equator at a constant speed and completes its annual course in the same amount of time the real sun takes at variable speeds
Copernican system
(astronomy) Copernicus' astronomical model in which the Earth rotates around the sun
Ptolemaic system
(astronomy) Ptolemy's model of the universe with the Earth at the center
(particle physics) a theory that involves an eleven-dimensional universe in which the weak and strong forces and gravity are unified and to which all the string theories belong
string theory
(particle physics) a theory that postulates that subatomic particles are one-dimensional strings
given, precondition, presumption
an assumption that is taken for granted
basic assumption, constatation, self-evident truth
an assumption that is basic to an argument
stochastic process
a statistical process involving a number of random variables depending on a variable parameter (which is usually time)
Type of:
concept, conception, construct
an abstract or general idea inferred or derived from specific instances

n a proposal intended to explain certain facts or observations

Type of:
something proposed (such as a plan or assumption)

n a message expressing an opinion based on incomplete evidence

conjecture, guess, speculation, supposition, surmisal, surmise
successful conjecture by unusual insight or good luck
Type of:
opinion, view
a message expressing a belief about something; the expression of a belief that is held with confidence but not substantiated by positive knowledge or proof

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