A (scientific) theory is simply a collection of many interlocked observations and logical deductions. A theory can be well established (such as Newton's theory

A (scientific) theory is simply a collection of many interlocked observations and logical deductions. A theory can be well established (such as Newton's theory of gravity, or the germ theory of disease), or it can still be at a hypothesis level (such as string theory) or it can be debunked (such as the humor imbalance theory of disease, or the geocentric theory of astronomy).