 First, notice that the étale topology is finer than the Zariski topology.Consequently, to define an étale cover of a scheme "X", it suffices to first cover "X" by open affine subschemes, that is, to take a Zariski cover, and then to define an étale cover of an affine scheme.An étale cover of an affine scheme "X" can be defined as a surjective family {"u"α