static) one, in that it can coexist in the same program with one external definition and any number of internal and inline definitions of the same function in other translation units, all of which can differ. This is a separate consideration from the linkage of the function, but not an independent one. C compilers are afforded the discretion to choose between using inline and external definitions of the same function when both are visible.
This refers to a function's ability to be defined both internally and externally, allowing multiple definitions within the same program, each potentially differing in implementation. This is distinct from how functions are linked together but not independent of that linkage. C compilers have the freedom to choose between inline and external definitions for the same function when both are visible.