What x belongs to if not all $x_i$ belong to $\mathbb R$?

Question

We know if all $x_i$ belong to $\mathbb R$, then we can say $x$ belongs to $\mathbb R^n$. But if $x_n$ does not belong to $\mathbb R$, then what can we say about $x$?

$x= \begin{bmatrix}x_1 \\ x_2 \\ \vdots \\ x_n\end{bmatrix} $

Answer 1

Let's say $x_n\in X$ where $X$ is any set. Then we can say $x\in \mathbb R^{n-1}\times X$ if it can help in the context you are working in.