What term describes a scientifically valid explanation for a given phenomenon?

The term that describes a scientifically valid explanation for a given phenomenon is a theory. In the context of scientific inquiry, a theory is an established framework that has been rigorously tested and validated through extensive observation and experimentation. It integrates a wide range of evidence and data to provide a comprehensive understanding of a particular aspect of the natural world.

Theories are distinguished by their robustness and ability to explain and predict natural phenomena. For example, the theory of evolution explains the diversity of life and is supported by genetic, fossil, and observational evidence. Unlike a hypothesis, which is a preliminary and testable statement about a relationship or phenomenon and typically requires further investigation, a theory stands on a solid foundation of accumulated evidence and has withstood critical scrutiny over time.

In contrast, principles are well-accepted rules that describe consistent relationships observed in nature but may not provide a comprehensive explanation for the underlying mechanisms, whereas assumptions are accepted premises that are taken for granted in the absence of proof.