easy
Our theory was that the plant needed more sunlight.
What does Theory mean?
an explanation idea based on evidence or reasoning.
Dictionary definition
A theory is an explanation or organized idea used to understand why something happens, often based on evidence and reasoning.
Example sentences
Theory in a sentence
medium
The detective tested each theory against the clues.
hard
In science, a strong theory explains many observations and is supported by evidence.
Writing practice
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Quick practice
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Practice the meaning of Theory
Answer three quick questions about its meaning and related words.
Question 1 of 3
Practice 1
What does theory mean?
A theory helps explain something using evidence and reasoning.
Practice 2
Which word is closest in meaning to theory?
Explanation is close in meaning to theory in this dictionary entry.
Practice 3
Which word is an antonym of theory?
Fact contrasts with theory in this dictionary entry.
Practice complete
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Pronunciation coach
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Theory
Voice settings
Sounds like
theer · ee · strongest beat: theer
Tap each sound part, then blend the whole word together.
Learn
WordTheory.
Partnoun.
MeaningTheory means an explanation idea based on evidence or reasoning.
ExampleExample: Our theory was that the plant needed more sunlight.
Word breakdown
2 syllables. Say each part, then blend the word.
- Syllables
- theer · ee
- Strongest beat
- theer
- Ending
- ee
- Tip
- Put a little extra energy on theer.
Your turn
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Synonyms
Words like Theory
explanationAn idea that tells why something happens.
hypothesisA testable idea that may explain something.
ideaA thought or possible explanation.
Antonyms
Opposite words
factSomething known to be true, not just an explanation.
random guessAn idea without evidence or reasoning.
Synonym practice
Want to practice theory synonyms in context? Try a Synonym Search question like "Our theory was that the plant needed more sunlight," then compare close word choices. Practice theory synonyms.
Word family
Theory word family
Base word
theory
noun
theory
An explanation based on evidence or reasoning.
noun
theories
More than one theory.
adjective
theoretical
Related to ideas or theories.
Related words
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Student support
Understand Theory
Hint for students
an explanation idea based on evidence or reasoning.
Common mix-up
Theory is not the same as fact. Theory means an explanation idea based on evidence or reasoning.
Try it in class or at home
Read this model sentence: The detective tested each theory against the clues. Clue words: detective, tested, each. Underline clue words that show why theory fits instead of fact. Now write one new sentence that shows theory without using the word theory. Ask: Does my sentence clearly show theory?
Teacher prompt
Ask students to explain this model sentence: "The detective tested each theory against the clues." Why does theory fit better than fact?
Learning activities
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