- closed Riemann surface
- closed ring
- closed scheme
- closed season
- closed semicircle
- closed semigroup
- closed semisphere
- closed sentential formula
- closed sequence
- closed set
- closed set basis
- closed-shelf book selling
- closed shell
- closed shell ion
- closed-shell ion
- closed shell molecule
- closed simplex
- closed solid sphere
- closed solution
- closed space
- closed sphere
- closed star
- closed string
- closed subalgebra
- closed subbase