theory
- 01 B2 Upper Intermediate
a well-tested explanation that uses facts to show how a part of the natural world works.
a coherent set of propositions used as principles of explanation for a class of phenomena, typically confirmed through observation or experiment.
Simple“In school, we studied the theory of evolution and how species change over time.”
In context“The general theory of relativity fundamentally altered our understanding of space, time, and gravity within the physical sciences.”
UsageOften used with 'of' followed by the subject of study.
Synonyms - 02 B2 Upper Intermediate
the rules and ideas of a subject, rather than the actual doing of it.
the body of rules, ideas, and principles of a particular subject or skill as distinguished from its practical application.
Simple“The course covers both music theory and how to play the piano.”
In context“While the candidate understood the theory of management, he struggled with the practical realities of leading a large team.”
SynonymsAntonyms - 03 B1 Intermediate
an idea that someone has to explain something, even if it is not proven yet.
a hypothesis, conjecture, or individual opinion offered as an explanation for an event.
Simple“I have a theory that the cat only meows when she wants treats.”
In context“Detectives are working on a theory that the two robberies were committed by the same group of people.”
Teacher's tipIn casual conversation, 'theory' is often used where a scientist would prefer 'hypothesis' or 'guess'.
- 04 C1 Advanced
a set of rules and statements that are logically connected to each other.
a set of axioms and all the statements that can be logically derived from them within a formal system.
Simple“The professor explained how set theory forms the basis of modern mathematics.”
In context“In model theory, we investigate the relationship between formal languages and their interpretations in various mathematical structures.”
Synonymsformal systemaxiomatization
Usage alternative theory · apply theory · build theory
From Middle French théorie, from Late Latin theōria, from Ancient Greek θεωρία (theōría, “contemplation, divine perspective, speculation, a looking at, a seeking”), from θεωρέω (theōréō, “I look at, view, see, consider, examine”), from θεωρός (theōrós, “spectator”), from θέα (théa, “view, perspective, sight”) + ὁράω (horáō, “I see, look”) [i. e. θέαν ὁράω (théan horáō, “see, look at a view; survey + genitive”)].
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.