The Grothendieck pretopology named after this value posits the existence of fibered products. Theseparation axiom named after this value holds for a topological space if for all pairs of distinct points,there exists an open set containing one but not the other. That separation axiom is sometimes namedafter Kolmogorov. The sphere S2 and the disc both have this genus and Euler characteristic. Allcountable sets have a (*) Hausdorff Dimension equal to this value. For a well-defined metric function tobe equal to this value, both of the inputs must be the same element of the topological space. This valueis also the dimension of a point. For 10 points, identify this value, 
The Grothendieck pretopology named after this value posits the existence of fibered products. Theseparation axiom named after this value holds for a topological space if for all pairs of distinct points,there exists an open set containing one but not the other. That separation axiom is sometimes namedafter Kolmogorov. The sphere S2 and the disc both have this genus and Euler characteristic. Allcountable sets have a (*) Hausdorff Dimension equal to this value. For a well-defined metric function tobe equal to this value, both of the inputs must be the same element of the topological space. This valueis also the dimension of a point. For 10 points, identify this value, which when added to a number equalssaid number.
The Grothendieck pretopology named after this value posits the existence of fibered products.
zero or 0