Meaning & use
theory
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Meanings
nouncountable
A well-tested explanation of how some part of the world works, built on evidence and able to predict results.
Grammar: Often with of: the theory of evolution.
Patterns
- the theory of something
- a theory about something
Einstein's theory of relativity changed how we think about space and time.
Scientists have tested the theory many times.
The theory explains why the planets move as they do.
noununcountable
A set of general principles or ideas on which a subject is based, as opposed to practice.
Grammar: Often contrasted with practice: in theory.
Patterns
- in theory
- theory and practice
In theory the plan works, but practice is different.
The course covers music theory and performance.
She studied economic theory before taking a job in finance.
nouncountableinformal
An idea or guess about why something happened, often with little proof.
Grammar: Informal use: my theory is that.
Patterns
- my theory is that
- a theory about something
My theory is that the cat knocked the vase over.
Police are exploring several theories about the fire.
He has a theory about why the bus is always late.
Word forms
| plural | theories |
|---|
Common combinations
- in theory
- In theory, the trains run every ten minutes.
- scientific theory
- A scientific theory must be testable.
- conspiracy theory
- He spread a conspiracy theory online.
- test a theory
- They tested the theory with an experiment.
- support a theory
- The data support the theory.
- in theory and in practice
- The rule works in theory and in practice.
Synonyms and how they differ
- hypothesis
- A hypothesis is a proposed explanation still waiting to be tested, whereas a scientific theory has already passed many tests.
- idea
- Idea is very general and carries no suggestion of evidence, while theory suggests an organized explanation.
- principle
- A principle is a basic rule or truth, whereas a theory explains how a range of facts fit together.
- hunch
- Hunch is a feeling without proof, which is weaker than even the informal use of theory.
Opposites
Word family
- theoretical adjective
- based on theory rather than practice
- theoretically adverb
- in theory, although perhaps not in practice
- theorize verb
- to form a theory about something
- theorist noun
- a person who develops theories
Commonly confused: theory or hypothesis?
theory vs hypothesis
A hypothesis is a first, untested explanation, while a scientific theory is supported by a great deal of evidence.
Practice
Which word best completes: 'A scientific ______ is supported by a large body of tested evidence, unlike a simple guess.'
Choose one answer.
In science, a theory is a well-tested explanation. A hunch, rumor or opinion lacks that backing.
Make it your own
Write a sentence using “theory”, then check it and compare it with the examples above.