2-sided

In mathematics, specifically in topology of manifolds, a compact codimension-one submanifold of a manifold is said to be 2-sided in when there is an embedding with for each and . In other words, if its normal bundle is trivial. This means, for example that a curve in a surface is 2-sided if it has a tubular neighborhood which is a cartesian product of the curve times an interval. A submanifold which is not 2-sided is called 1-sided. rdf:langString