physics, mathematical physics, philosophy of physics
theory (physics), model (physics)
experiment, measurement, computable physics
Axiomatizations
Tools
Structural phenomena
Types of quantum field thories
Physics studies the constituting mechanisms of the observable universe.
Starting with suggestions by Galileo around 1600 and then clearly so since Newton in 1687 laid the foundations of physics proper with what is since called Newton's laws of physics, distinguishing it from the earlier natural philosophy, physics is specifically concerned with modelling experimentally observed phenomenology by “physical laws” formulated in the language of mathematics.
Philosophy$[$i.e. physics $]$ is written in this grand book — I mean the universe — which stands continually open to our gaze, but it cannot be understood unless one first learns to comprehend the language and interpret the characters in which it is written. It is written in the language of mathematics, and its characters are triangles, circles, and other geometrical figures, without which it is humanly impossible to understand a single word of it; without these, one is wandering around in a dark labyrinth. (Galileo Galilei in Galilei, Il Saggiatore, 1623).
The relation to mathematics is typically the stronger the more one turns to fundamental physics (e.g. fundamental particles) and away from complex systems or else the more one coarse-grains irregular complex behaviour and studies statistical aspects in statistical physics.
The present most fundamental understanding of the physics of the observable universe is summarized in models (in theoretical physics) called
which are formulated in the two fundamental theories called
which in turn are both instances of the general framework of classical/quantum field theory.
Theoretical physics also studies lots of approximate, hypothetical “toy”- and test-case models (in theoretical physics), exploring the “space of physical theories”, and parts of mathematical physics overlaps with pure mathematics, the relation to physics only serving as a motivation that may or may not eventually lead back to statements about phenomenology.