# theory

Pronunciation: say "THEER-ee" US /ˈθɪ.ɹi/, UK /ˈθɪə.ɹi/

## Noun

1. An idea or explanation put forward for why something happens or how something works, especially one that has not been proved.
   - Simple: An idea that explains why something happens or how something works, often one that has not been proved.
   - _She had a theory that the missing keys had slipped down behind the car seat._
   - _His theory about the strange noise turned out to be completely wrong._
2. A coherent set of ideas that explains observed facts, correctly predicts new ones, and has been confirmed by observation and experiment.
   - Simple: A well-tested explanation that fits the known facts and correctly predicts new ones.
   - _Darwin's theory of evolution explains how species change over time._
   - _Once enough evidence supported it, the theory became widely accepted among researchers._
3. The principles and established methods of a subject, skill, art, or game, as opposed to putting them into practice.
   - Simple: The ideas, rules, and methods behind a subject, skill, or game, rather than actually doing it.
   - _He understood the theory of painting long before he picked up a brush._
   - _In medical training, theory and hands-on practice are taught side by side._
4. A field of study that attempts to describe a particular class of constructs as fully as possible.
   - Simple: A branch of study that tries to fully describe one kind of thing.
   - _Mathematicians developed an entire theory to describe this class of objects._
   - _Number theory concerns itself with the deep properties of the integers._
5. A set of axioms together with all the statements that can be derived from them.
   - Simple: In logic, a set of basic rules and everything that can be proved from them.
   - _Every theory in first-order logic is closed under logical consequence._
   - _They proved that the theory was consistent._

## Noun

6. The mental act of conceiving something; reflection or careful consideration. *(obsolete)*
   - Simple: The act of thinking deeply or reflecting on something.

## Origin

The word came through Middle French théorie and Late Latin theōria from Ancient Greek θεωρία (theōría, "contemplation, speculation, a looking at"), which derives from θεωρέω (theōréō, "I look at, view, consider") and ultimately from θεωρός (theōrós, "spectator"), formed from θέα (théa, "view, sight") and ὁράω (horáō, "I see, look").

Source: DictionaryAI, https://dictionaryai.com/define/theory (written from Wiktionary data, CC BY-SA 4.0: https://creativecommons.org/licenses/by-sa/4.0/).