theory
/ˈθɪəri/ (bre, ipa) · /ˈθiːəri/ (ame, ipa) · /ˈthē-ə-rē ˈthir-ē/ (ame, mw)
theory — noun
- theorysingular
- theoriesplural
1. a set of well-tested ideas that explains why something happens in nature or soci
a set of well-tested ideas that explains why something happens in nature or society, based on evidence and careful study
Darwin's theory of evolution explains how species gradually adapt to changing environments.
collocation: theory of [something]
Noa tested the theory by measuring water temperature at different depths.
transitive use: test a theory
Élise wrote her thesis on a theory about how children learn their first language.
According to the Big Bang theory, the universe began with an enormous explosion.
Takeshi's experiment supported the theory that sleep helps strengthen new memories.
- hypothesis
a proposed but not yet fully tested explanation — narrower and more tentative than a theory
- model
a simplified representation used to analyse or predict a system — often more concrete and specific
- framework
a basic structure of ideas that supports further thinking — broader and less formal than a scientific theory
- doctrine
a set of beliefs held and taught by a group — often implies authority or ideology rather than empirical testing
文法句型
theory of [something]
theory that [clause]
[verb] + theory
用法筆記
Commonly constructed with 'of' ('theory of relativity') or a 'that'-clause ('the theory that...'). In everyday English, 'theory' is sometimes used loosely to mean 'an untested guess,' but in academic and scientific contexts it refers to a well-supported explanatory framework supported by evidence.
常見錯誤
2. applies when something should be possible according to an idea or system, but in
applies when something should be possible according to an idea or system, but in reality it often works out differently
In theory, the faster computer should finish the task in half the time.
adverbial phrase: 'in theory' at start of sentence
The new policy makes sense in theory, but it is hard to put into practice.
contrast pattern: 'in theory, but...'
Roya knew that in theory all the data was safe, yet she still made backups.
In theory, raising taxes should reduce pollution, but some experts disagree.
Rafael agreed with the idea in theory, though he worried about the cost.
- in principle
similar meaning but slightly more formal, focusing on the underlying concept rather than a hypothetical scenario
- theoretically
adverb form that can replace the phrase 'in theory' in most contexts
- in practice
the most direct contrast — what actually happens versus what is supposed to happen
- in reality
similar to 'in practice', emphasizing the real-world outcome rather than the expected one
文法句型
in theory
in theory ... but in practice / in reality
用法筆記
The phrase 'in theory' is the most common form of this sense; the adverb 'theoretically' can be used in the same way ('Theoretically, the machine should work'). The contrast pattern 'in theory...but in practice/reality...' is especially frequent in discussions of plans, policies, and proposals.