The definition of  physics  is the study of the physical plane of matter, motion, force, and energy. The root word of physics is  Phys-  and is Greek for "nature" and "natural order." Physics itself is studying the natural world and the interactions between objects and energy in any given environment.  Broadly, physics involves the study of everything in physical existence, from the smallest subatomic particles to the entire universe. Physicists try to develop conceptual and mathematical models that describe interactions between entities (both big and small) and that can be used to extend our understanding of how the universe works at different scales.