In science, a law is defined as a concise, verbal or mathematical, statement that summarizes a vast number of experimental observations. It describes or predicts some facets of the natural world that always remain the same under the same conditions.
A scientific theory is a unifying principle that provides a well-substantiated and testable explanation of aspects of nature and provides the reason for why things happen. Well-established theories are the pinnacle of scientific knowledge that has been developed over many years of constant experimental evaluation; they are as close to the truth as we get in science. They, too, are continuously tested and modified with newer observations obtained through advancements in science and technology.
Thus, while a hypothesis is a proposed explanation for a particular observation, a theory is a well-tested explanation for a broad set of observations that explain a particular facet of the physical world around us. Scientific laws are statements about particular observations; they do not explain the reason involved.
This text is adapted from Openstax, Chemistry 2e, Section 1.1: The Scientific Method.
