Please let me denote the following - (TOP) topological manifolds https://en.wikipedia.org/wiki/Topological_manifold - (PDIFF), for piecewise differentiable https://en.wikipedia.org/wiki/PDIFF - (PL) piecewise-linear manifolds https://en.wikipedia.org/wiki/Piecewise_linear_manifold#Smooth_manifolds - (DIFF) the smooth manifolds https://en.wikipedia.org/wiki/Differentiable_manifold#Definition - (TRI) triangulable manifolds https://en.wikipedia.org/wiki/Triangulation_%28topology%29 we consider the **category** of manifolds and their maps based on what I learned from Wikipedia above links. Is it true that the above **categories** have the following relations: >(1) TOP $\supseteq$ TRI ? > > Namely, every TRI must be TOP manifolds? > >(2) TRI $\supseteq$ PL ? > > Namely, every PL must be TRI manifolds? > >(3) TRI $\supseteq$ DIFF ? > > Namely, every DIFF must be TRI manifolds? > >(4) PL $\supseteq$ DIFF ? > > Namely, every DIFF must be PL manifolds? > > (5) So in a short summary, is it true that > >$$\text{ TOP $\supseteq$ TRI $\supseteq$ PL $\supseteq$ DIFF} ?$$ (If what I said in (5) is false, what are their intersections, unions and complements of these categories?) p.s. This is based on an improved unanswer question from MSE a week ago. I am sorry I hope more experts can fill in this question. Thanks! <3