High Quality Content by WIKIPEDIA articles! In topology, the Tychonoff plank is a topological space that is a counterexample to several plausible-sounding conjectures. The Tychonoff plank is a compact Hausdorff space and is therefore a normal space. However, the deleted Tychonoff plank is non-normal. Therefore the Tychonoff plank is not completely normal. This shows that a subspace of a normal space need not be normal. The Tychonoff plank is not perfectly normal because it is not a G? space: the singleton {infty} is closed but not a G? set.

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