Definitions

theory

[thee-uh-ree, theer-ee] / ˈθi ə ri, ˈθɪər i /

NOUN

hypothesis, belief

Synonyms

STRONGEST

approach argument assumption code concept doctrine idea ideology method philosophy plan position premise proposal provision rationale scheme speculation suspicion system thesis understanding

STRONG

base basis codification conditions conjecture dogma feeling foundation grounds guess guesswork hunch impression outlook postulate presentiment presumption shot stab supposal supposition surmise theorem

WEAK

formularization suppose systemization

Antonyms

STRONGEST

disbelief fact information reality truth

STRONG

calculation knowledge measurement proof

WEAK

certainty

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Quantum mechanics governs nature at the smallest scales such as particles, while Einstein’s theory of general relativity applies to gravity and spacetime.

From Science Daily • May 22, 2026

One theory is that GLP-1s reduce cancer risk indirectly—by driving weight loss and improving metabolic health, both of which are independently linked to lower cancer rates.

From The Wall Street Journal • May 21, 2026

"The homicide theory does not hold up," said his lawyer, Cristóbal Martell.

From BBC • May 20, 2026

Justice Neil Gorsuch seemed particularly aware of how expansive the government’s theory could become.

From Slate • May 20, 2026

If you got your ISDA, you could in theory trade with the big Wall Street firms, if not as an equal then at least as a grown-up.

From "The Big Short" by Michael Lewis

Vocabulary lists containing theory

The Vocabulary.com Top 1000

Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!

The SAT: Language of the Test, List 6

Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!

The New SAT: The Language of the Test

Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!