- closed-flux device
- closed fork mounting
- closed form
- closed-form number
- closed-form solution
- closed formula
- closed fuel cycle
- closed function
- closed geodesic
- closed graph
- closed-graph mapping
- closed graph theorem
- closed-graph theorem
- closed grill
- closed ground field
- closed group
- closed half-line
- closed half-plane
- closed half space
- closed half-space
- closed-head foam-water sprinkle system
- closed hyperplane
- closed hypersurface
- closed ideal
- closed image