Note that "spectrum" is an overloaded word. It also refers to the spectrum σ("x") of an element "x" of an algebra with unit 1, that is the set of complex numbers "r" for which "x" - "r" 1 is not invertible in "A". For unital C*-algebras, the two notions are connected in the following way: σ("x") is the set of complex numbers "f"("x") where "f" ranges over Gelfand space of "A". Together with the spectral radius formula, this shows that "Â" is a subset of the unit ball of "A*" and as such can be given the relative weak-* topology. This is the topology of pointwise convergence. A net {"f""k"}"k" of elements of the spectrum of "A" converges to "f" if and only if for each "x" in "A", the net of complex numbers {"f""k"("x")}"k" converges to "f"("x").