A dichotomy property for the graphs of monomials

We prove that the graph of a discontinuous $n$-monomial function $f:\mathbb{R}\to \mathbb{R}$ is either connected or totally disconnected. Furthermore, the discontinuous monomial functions with connected graph are characterized as those satisfying a certain big graph property. Finally, the connectedness properties of the graphs of additive functions $f:{\mathbb{R}}^d\to \mathbb{R}$ are studied.