What is the meaning of a theory in science?

In science, a theory is a well-substantiated explanation of some aspect of the natural world, based on a body of evidence and repeatedly tested hypotheses. It integrates and generalizes multiple observations and findings, providing a coherent framework for understanding phenomena. Unlike a mere guess or hypothesis, a scientific theory is robust and can be modified or refined as new evidence emerges. Examples include the theory of evolution and the theory of relativity, both of which have withstood extensive scrutiny and testing.