Electrical

Conductor ampacity and its derating for temperature and fill; grounding electrodes, conductors and grid resistance; short-circuit current; motor full-load amps; panel sizing, slot counts and phase balance; lighting circuits and illuminance; cable tray fill, weight and support; pulling tension; and the clearances and heat loads an electrical room has to allow for.

Which table governs. Almost nothing here is derived from first principles — it is a lookup with corrections, and the correction factors are the calculation. Each page names the code table it reads from, because an ampacity without its column and its derating is a number with no meaning.

The mechanical plant a circuit serves, the conduit's physical routing, and lightning protection beyond the rod count.