clopen

Etymology
.

Adjective

 * 1)  Both open and closed.
 * 2) * 1999, S. J. Dilworth, On the extensibility of certain homeomorphisms and linear isometries, Krzysztof Jarosz (editor), Function Spaces: Proceedings of the Third Conference on Function Spaces,, Contemporary Mathematics, Volume 232, page 124,
 * FACT 1. Disjoint closed subsets of $$\mathbb{N}^\mathbb{N}$$ may be separated by disjoint clopen sets.
 * FACT 1. Disjoint closed subsets of $$\mathbb{N}^\mathbb{N}$$ may be separated by disjoint clopen sets.

Noun

 * 1) A pair of work shifts in which a worker works a closing shift one day and then works an opening shift the following day.