Physical theory refers to a set of principles or laws that are used to explain physical phenomena. There are several synonyms that can be used to refer to physical theory, such as scientific theory, natural law, physical law, and laws of nature. Scientific theory is a general term used to describe theories developed by scientists to explain a wide range of phenomena. Natural law refers to a fundamental principle that is thought to underlie the workings of the natural world. Physical law is a general term used to describe principles governing the behavior of physical objects. Laws of nature are thought to be fundamental laws that describe the universe's behavior and can't be broken.