General topology Basic notions: open sets, neighbourhoods, bases Concept
Clopen set
Summary
A clopen set in a topological space is a subset that is both open and closed. The empty set and the whole space are always clopen. A space is connected exactly when it has no other clopen sets, so clopen sets measure how a space splits into pieces.
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| Tag | DQ4E55T3BW |
|---|---|
| URI | m2://DQ4E55T3BW |
| Kind | concept |
| Writing | W0 stub |
| MSC | 54A05, 54D05 |
| Same as | |
| Changed | 2 November 2026 |
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