Hello!
There is a simple line in the textbook.
If ##S## is a manifold, an injectively immersed submanifold ##M## of ##S## is embedded if and only if ##M## is locally closed in ##S##.
Recall the definition. M is locally closed if for each point ##x\in M## there open ##U\subset S## such that ##M\cap U## is closed in ##U##.
Embedding to injective immesion is simple. The opposite direction is hard.
Suppose I have ##N## as source manifold and ##f:N\rightarrow S## is the injective...