Physics is the science that studies matter and its motion and behavior through space and time, along with related concepts such as energy and force.[1] In modern usage, the term often refers to theoretical physics, a model-based, mathematical body of knowledge that forms the foundation of all the natural sciences (although in practice, some parts of physics—such as fluid mechanics and parts of thermodynamics—are engineering disciplines,[2][3] due to their heavy use in engineering).[4] Physics also addresses other questions about the nature of time, space, mass, and even the origins of the universe as a whole