the·o·ry

[thee-uh-ree, theer-ee]
noun, plural the·o·ries.
1.
a coherent group of tested general propositions, commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena: Einstein's theory of relativity. Synonyms: principle, law, doctrine.
2.
a proposed explanation whose status is still conjectural and subject to experimentation, in contrast to well-established propositions that are regarded as reporting matters of actual fact. Synonyms: idea, notion hypothesis, postulate. Antonyms: practice, verification, corroboration, substantiation.
3.
Mathematics. a body of principles, theorems, or the like, belonging to one subject: number theory.
4.
the branch of a science or art that deals with its principles or methods, as distinguished from its practice: music theory.
5.
a particular conception or view of something to be done or of the method of doing it; a system of rules or principles: conflicting theories of how children best learn to read.
6.
contemplation or speculation: the theory that there is life on other planets.
7.
guess or conjecture: My theory is that he never stops to think words have consequences.
Idioms
8.
in theory, ideally; hypothetically: In theory, mapping the human genome may lead to thousands of cures.
00:10
Theory is always a great word to know.
So is divide. Does it mean:
the operation or process of finding the difference between two numbers or quantities, denoted by a minus sign (?)
to separate into equal parts by the process of mathematical division
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Origin:
1590–1600; < Late Latin theōria < Greek theōría a viewing, contemplating, equivalent to theōr(eîn) to view + -ia -y3

Can be confused: hypothesis, law, theory (see synonym study at the current entry).

Synonym Study
1. Theory, hypothesis are used in non-technical contexts to mean an untested idea or opinion. A theory in technical use is a more or less verified or established explanation accounting for known facts or phenomena: the theory of relativity. A hypothesis is a conjecture put forth as a possible explanation of phenomena or relations, which serves as a basis of argument or experimentation to reach the truth: This idea is only a hypothesis.
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2013.
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World English Dictionary
theory (ˈθɪərɪ) [Click for IPA pronunciation guide]
 
—n , pl -ries
1.  a system of rules, procedures, and assumptions used to produce a result
2.  abstract knowledge or reasoning
3.  a speculative or conjectural view or idea: I have a theory about that
4.  an ideal or hypothetical situation (esp in the phrase in theory)
5.  a set of hypotheses related by logical or mathematical arguments to explain and predict a wide variety of connected phenomena in general terms: the theory of relativity
6.  a nontechnical name for hypothesis
 
[C16: from Late Latin theōria, from Greek: a sight, from theōrein to gaze upon]

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Etymonline
Word Origin & History

theory
1590s, "conception, mental scheme," from L.L. theoria (Jerome), from Gk. theoria "contemplation, speculation, a looking at, things looked at," from theorein "to consider, speculate, look at," from theoros "spectator," from thea "a view" + horan "to see." Sense of "principles or methods of a science or
art (rather than its practice)" is first recorded 1610s. That of "an explanation based on observation and reasoning" is from 1630s.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

theory the·o·ry (thē'ə-rē, thēr'ē)
n.

  1. A systematically organized body of knowledge applicable in a relatively wide variety of circumstances, especially a system of assumptions, accepted principles, and rules of procedure devised to analyze, predict, or otherwise explain the nature or behavior of a specified set of phenomena.

  2. Abstract reasoning; speculation.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
theory   (thē'ə-rē, thîr'ē)  Pronunciation Key 
A set of statements or principles devised to explain a group of facts or phenomena. Most theories that are accepted by scientists have been repeatedly tested by experiments and can be used to make predictions about natural phenomena. See Note at hypothesis.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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American Heritage
Cultural Dictionary

theory definition


In science, an explanation or model that covers a substantial group of occurrences in nature and has been confirmed by a substantial number of experiments and observations. A theory is more general and better verified than a hypothesis. (See Big Bang theory, evolution, and relativity.)

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Slang Dictionary

theory

n. The consensus, idea, plan, story, or set of rules that is currently being used to inform a behavior. This usage is a generalization and (deliberate) abuse of the technical meaning. "What's the theory on fixing this TECO loss?" "What's the theory on dinner tonight?" ("Chinatown, I guess.") "What's the current theory on letting lusers on during the day?" "The theory behind this change is to fix the following well-known screw...."
Jargon
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FOLDOC
Computing Dictionary

theory definition


The consensus, idea, plan, story, or set of rules that is currently being used to inform a behaviour. This usage is a generalisation and (deliberate) abuse of the technical meaning. "What's the theory on fixing this TECO loss?" "What's the theory on dinner tonight?" ("Chinatown, I guess.") "What's the current theory on letting lusers on during the day?" "The theory behind this change is to fix the following well-known screw...."
(1994-12-14)

The Free On-line Dictionary of Computing, © Denis Howe 2010 http://foldoc.org
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Example sentences
Barely a decade ago scientists who study how planets form had to base their
  theory on a single example-our solar system.
Common game theory has held that punishment makes two equals cooperate.
Of course, there is a big gap between theory and practice.
But this pairing theory does not hold for high-temperature copper-oxygen
  materials.
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