$\textbf{Banach space}$
A Banach space is a complete normed space, i.e.
- a vector space $X$ over the real or complex numbers $\mathbb{F}$ with a norm $\lVert\cdot\rVert_X$
- which is complete, i.e. for every Cauchy sequence $(x_n)$ in $X$, there exists an element $x$ in $X$ such that $$\lim_{n\to\infty}\lVert x_n-x\rVert_X=0$$
$\textbf{Banach space}$
A Banach space is a complete normed space, i.e.
- a vector space $X$ over the real or complex numbers $\mathbb{F}$ with a norm $\lVert\cdot\rVert_X$
- which is complete, i.e. for every Cauchy sequence $(x_n)$ in $X$, there exists an element $x$ in $X$ such that $$\lim_{n\to\infty}\lVert x_n-x\rVert_X=0$$