Definition of "theory" []

• A set of statements or principles devised to explain a group of facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomena. (noun)
• The branch of a science or art consisting of its explanatory statements, accepted principles, and methods of analysis, as opposed to practice: a fine musician who had never studied theory. (noun)
• A set of theorems that constitute a systematic view of a branch of mathematics. (noun)
• Abstract reasoning; speculation: a decision based on experience rather than theory. (noun)
• A belief or principle that guides action or assists comprehension or judgment: staked out the house on the theory that criminals usually return to the scene of the crime. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Thermodynamic laws are unified with mechanical theory through an *application of information theory*."
• "I must be a dinosaur too--maybe even more of one, because I have a similar problem even with articles that purport to be about a piece of literature but are really about theory--and only use literature to prove the *theory* correct."
• "This theory, it should be remembered, is _merely a theory_, _a mere notion_, _a hypothesis_."