What are the two meanings of static in C?

They're unrelated and depend on placement. Inside a function, static gives a local variable persistent lifetime: it's allocated in .data/.bss rather than on the stack, initialized exactly once, and retains its value across calls, but its name is still scoped to that function. At file scope, static on a global variable or function gives internal linkage: the symbol is private to its translation unit and invisible to the linker from other .c files, which is C's primary encapsulation mechanism for hiding implementation details and avoiding name collisions. So "static local" = lifetime, "static global/function" = visibility. The shared thread is "static storage duration," but the practical effect you reason about differs by context.