As for 1α, you can think of it as the fourth generation of the 10nm class where the half-pitch ranges from 10 to 19nm. As we go from 1x nanometer to 1y, 1z and 1α, this dimension gets smaller and smaller. We started with 1x, but as we continued to shrink and name the next nodes, we hit the end of the roman alphabet. That’s why we switched to the Greek alphabet alpha, beta, gamma and so on.