The space $C^{\omega}(\Omega)$ of real-valued real analytic functions on the open bounded set $\Omega\subset \mathbb R^n$ does not have any obvious or natural metric which would make it a Fréchet space.
I am wondering if there is a way to define a norm on the space of real analytic real-valued functions defined on $\mathbb{R}^n$, even if not in a canonical way.