Kra
tchik, M.B. 克赖希克（1882—1957）
- organization
- OR gate
- oricycle
- orientability
- orientability of a manifold
- orientable
- orientable bundle
- orientable contour
- orientable development
- orientable fiber bundle
- orientable foliation
- orientable homology class
- orientable homology manifold
- orientable hypersurface
- orientable manifold
- orientable polygon
- orientable polyhedron
- orientable space
- orientable submanifold
- orientable surface
- orientation
- orientation class
- orientation cohomology class
- orientation homology class
- orientation manifold