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We found 58 dictionaries with English definitions that include the word theory:
Click on the first link on a line below to go directly to a page where "theory" is defined.

General (30 matching dictionaries)

1. theory: Merriam-Webster.com [home, info]
2. theory: Oxford Dictionaries [home, info]
3. theory: American Heritage Dictionary of the English Language [home, info]
4. theory: Collins English Dictionary [home, info]
5. theory: Vocabulary.com [home, info]
6. theory: Macmillan Dictionary [home, info]
7. Theory, theory: Wordnik [home, info]
8. theory: Cambridge Advanced Learner's Dictionary [home, info]
9. theory: Wiktionary [home, info]
10. theory: Webster's New World College Dictionary, 4th Ed. [home, info]
11. theory: The Wordsmyth English Dictionary-Thesaurus [home, info]
12. theory: Infoplease Dictionary [home, info]
13. theory: Dictionary.com [home, info]
14. theory: Online Etymology Dictionary [home, info]
15. theory: UltraLingua English Dictionary [home, info]
16. theory: Cambridge Dictionary of American English [home, info]
17. Theory (brand), Theory (clothing retailer), Theory (disambiguation), Theory (mathematical logic), Theory (science), Theory: Wikipedia, the Free Encyclopedia [home, info]
18. Theory: Online Plain Text English Dictionary [home, info]
19. theory: Webster's Revised Unabridged, 1913 Edition [home, info]
20. theory: Rhymezone [home, info]
21. theory: AllWords.com Multi-Lingual Dictionary [home, info]
22. theory: Webster's 1828 Dictionary [home, info]
23. theory: Free Dictionary [home, info]
24. theory: Mnemonic Dictionary [home, info]
25. theory: WordNet 1.7 Vocabulary Helper [home, info]
26. theory: LookWAYup Translating Dictionary/Thesaurus [home, info]
27. theory: Dictionary/thesaurus [home, info]
28. theory: Wikimedia Commons US English Pronunciations [home, info]

Art (3 matching dictionaries)

29. theory: ArtLex Lexicon of Visual Art Terminology [home, info]
30. theory: The Organon: A Conceptually Indexed Dictionary (by Genus and Differentia) [home, info]
31. theory: Literary Criticism [home, info]

Business (2 matching dictionaries)

32. theory: Legal dictionary [home, info]
33. theory: BusinessDictionary.com [home, info]

Computing (3 matching dictionaries)

34. theory: Free On-line Dictionary of Computing [home, info]
35. Theory: Cybernetics and Systems [home, info]
36. Theory (mathematical logic), theory: Encyclopedia [home, info]

Medicine (2 matching dictionaries)

37. theory: online medical dictionary [home, info]
38. theory: Medical dictionary [home, info]

Miscellaneous (3 matching dictionaries)

39. theory: Sociology [home, info]
40. theory: A Brief Critical Dictionary of Education [home, info]
41. theory: Idioms [home, info]

Science (13 matching dictionaries)

42. Theory: Misunderstood Physics Terms [home, info]
43. theory: Archaeology Wordsmith [home, info]
44. Theory: Bird On! [home, info]
45. Theory: Eric Weisstein's World of Mathematics [home, info]
46. Theory: Eric Weisstein's World of Physics [home, info]
47. - - Theory, Theory: Extragalactic Astronomy [home, info]
48. theory: General Chemistry Online [home, info]
49. theory: Evolution Glossary [home, info]
50. theory, theory, theory: PlanetMath Encyclopedia [home, info]
51. Theory: Physic and Astronomy Glossary [home, info]
52. theory: Anthropological Terms [home, info]
53. theory: Anthropology dictionary [home, info]
54. theory: FOLDOP - Free On Line Dictionary Of Philosophy [home, info]

Slang (1 matching dictionary)

55. Theory: Urban Dictionary [home, info]

Tech (1 matching dictionary)

56. theory: Webster's New World Telecom Dictionary [home, info]

(Note: See theorys for more definitions.)

Quick definitions from Macmillan ( ) Provided by Quick definitions from WordNet (theory) ▸ noun:  a belief that can guide behavior ("The architect has a theory that more is less") ▸ noun:  a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena ("True in fact and theory") ▸ noun:  a tentative theory about 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") ▸ Also see theorys ▸ Word origin ▸ Words similar to theory ▸ Usage examples for theory ▸ Popular adjectives describing theory ▸ Words that often appear near theory ▸ Rhymes of theory ▸ Invented words related to theory