General topology Connectedness Counterexample
Comb space
Builds on Path-connected spaceLocally connected spaceLocally path-connected space
Counterexample
Let . The comb space is the subspace of It consists of a base segment, the tooth , and the teeth .
The space is path-connected. Each point can be joined to by going down its tooth and then along the base.
The space is not locally connected. Take and the open set . For large , the set contains a piece of the tooth near height . Any open set with contains such pieces, but contains no part of the base. The vertical line with strictly between two teeth splits into two disjoint open parts, one of them containing . So no open neighbourhood of inside is connected.
Remarks
So connectedness, even path-connectedness, does not imply local connectedness. For the same reason, is not locally path-connected. The comb space is contractible, so it also shows that contractible spaces need not be locally connected.
Reading path
To understand this page from the ground up, read these 4 pages in order. The foundations come first.
Show the path as a graph
- no evidence level
- Locally connected space concept
- Locally path-connected space concept
- Path-connected space concept
- Comb space counterexample
Further reading
About this page
| Tag | A2Q4RXD162 |
|---|---|
| URI | m2://A2Q4RXD162 |
| Kind | counterexample |
| Writing | W0 stub |
| MSC | 54G20, 54D05 |
| Uses | Path-connected space, Locally connected space, Locally path-connected space |
| Same as | |
| Changed | 2 November 2026 |
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