# Tame submanifold

Let $M$ be a manifold of dimension $m$ and $N$ a submanifold of dimension $n$. Then $N$ is termed tame in $M$ if for every point $x \in N$, there exists a neighbourhood $U$ of $x$ in $M$ such that the pair $(U, U \cap N)$ is homeomorphic to the pair $(\R^m,\R^n)$ where $\R^n$ is viewed as a linear subspace of $\R^m$.
An example of a submanifold which is not tame is the Alexander horned sphere in $\R^3$.