(a) This shows three two-dimensional square lattices, stacked on top of one another to give a three-dimensional lattice with a cubic unit cell.
(b) This shows a cubic unit cell, with cell edges labelled a, b and c and three crystallographic axes labelled x, y and z parallel to the cell edges.
Axis x is parallel to a, axis y is parallel to b and axis z is parallel to c.
(c) This shows the relationship between the three crystallographic axes and their interaxial angles.
Alpha is the angle between y and z, beta the angle between x and z and gamma the angle between x and y.