The use of the term 'dimension' to descibe arrays and vectors

This is not a math tutorial. See Why am I writing about math?

In math, computer science, and machine learning, the meaning of the term dimension depends on the context. When describing arrays/matrices, dimensionality refers to the indices. For example, the following array is a 2D array. It has 4 rows and 3 columns:

array([[0., 0., 0.],
       [0., 0., 0.],
       [0., 0., 0.],
       [0., 0., 0.]])

If the same array is interpreted as vectors, each row is a 3D vector, and each column is a 4D vector.