A well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.

Here's why:

* Well-substantiated: Theories are not just guesses. They are backed by a large body of evidence from multiple sources.

* Explanation: Theories don't just describe what happens; they attempt to explain why it happens.

* Natural world: Scientific theories focus on the natural world and its phenomena.

* Incorporates facts, laws, inferences, and tested hypotheses: Theories are built upon a foundation of established scientific knowledge.

It's important to note that scientific theories are not absolute truths. They are the best current explanations based on available evidence, and they can be modified or even replaced as new evidence emerges.