What is "submanifold"

n. (context topology English) A manifold which is a subset of another, so that the inclusion function is an embedding or, sometimes, an immersion

In mathematics, a submanifold of a manifold M is a subset S which itself has the structure of a manifold, and for which the inclusion map S → M satisfies certain properties. There are different types of submanifolds depending on exactly which properties are required. Different authors often have different definitions.