theory
nounUK /ˈθɪə.ri/
US /ˈθɪr.i/
A theory is a careful idea that explains how or why something happens.
The scientist has a theory about why the dinosaurs disappeared.
SYNONYMS
RELATED WORDS
OTHER MEANINGS
2. A set of rules or ideas used to understand a subject.
She is studying music theory at college.
3. An opinion or guess that may or may not be true.
My theory is that he forgot his keys at home.
4. A well-tested explanation in science that many facts support.
The theory of gravity explains why apples fall to the ground.