In science, physics is the study of the laws that determine the structure of the universe with reference to the matter and energy of which it consists. It is concerned with the forces that exist between objects and the interrelationship between matter and energy. 
The term physis (φύσις), supposedly, comes from phyein (φύειν), "to grow", related to our word "be"; possibly deriving from Thales. (Ѻ)
In 320BC, Aristotle introduced term "physics", in parallel with "metaphysics", as the study of things, in short.
In circa 1610, Francis Bacon, building on Aristotle, defined physics, a sub-branch of philosophy, as follows: 
PhilosophyIn 1830s, the word “physicist” began to appear in English, e.g. as used in the Whewell-Coleridge debate (1833). 1. Divine philosophy
2. Natural philosophy2.1. Speculative philosophy (or natural science)2.1.1. Physics126.96.36.199. The doctrine of the formation of things188.8.131.52. The doctrine of the formation of things, or the world184.108.40.206. The doctrine concerning the variety of things [metamorphosis or evolution]2.1.2. Metaphysics3. Human philosophy2.2. Practical philosophy220.127.116.11. The doctrine of forms
18.104.22.168. The doctrine of final causes