Order is not rank

⚠️ The word rank has two different meanings, and they collide.

In linear algebra, rank means the number of independent columns of a matrix. In tensor theory, rank often means the number of axes. To avoid the confusion, this workshop says order for the number of axes, and uses rank only in the linear-algebra sense.

The practical difference: order is the length of the shape tuple and the shape gives it away. Rank counts independent directions and has to be computed, with np.linalg.matrix_rank.