noun
covering space
A topological concept: a space that maps onto another space such that each point has a neighborhood whose preimage is a disjoint union of homeomorphic copies. Used in algebraic topology and related fields.
被覆空間の理論は基本群の研究で重要である。
The theory of covering spaces is important in the study of fundamental groups.
円周の普遍被覆空間は実数直線である。
The universal covering space of the circle is the real line.