physics
Physik is the German word for the scientific study of matter, energy, and the fundamental laws of the universe. It is used in the same way as the English word 'physics' and covers the same range of topics, from classical mechanics to quantum theory.
Physics is an interesting science.
This sentence states that physics, which is a field of scientific study, is considered interesting by the speaker.
I'm studying physics at the university.
This sentence communicates that the speaker is studying physics, a scientific area of knowledge, at a university.
The physics book is very heavy.
This sentence describes a physical attribute of a physics book. The speaker perceives it as heavy.