https://en.m.wikipedia.org/wiki/Compactness_theorem
(or if you like arcane ramblings some of whose fragments might suddenly make sense within a year, https://ncatlab.org/nlab/show/compactness+theorem)
https://en.m.wikipedia.org/wiki/Compactness_theorem
(or if you like arcane ramblings some of whose fragments might suddenly make sense within a year, https://ncatlab.org/nlab/show/compactness+theorem)