Definition
A matrix is a rectangular group of numbers (or symbols) with a given number of rows and columns.
Example
The following matrix has two rows and three columns, and is described as a "two by three" (2x3) matrix.
LaTeX
\begin{bmatrix} 3 & 6 & 2 \\ 5 & 1 & 10 \end{bmatrix}
Notation
 There are a few different ways to represent a matrix. The easiest is with an bold uppercase letter: A
Code
A = [[3, 6, 2], [5, 1, 10]] print(A)
Notes
 The plural of matrix is matrices.
 The size of a matrix is called its dimension or order. It is written with as rows x columns. A matrix with 2 rows and 3 columns is written as 2x3.

Two matrices are considered equal if and only if:
 They have the same number of rows.
 They have the same number of columns.
 Each corresponding element is equal. i.e. x1_{11} = x2_{11}

The
numpy.matrix is depreciated, in favour of regular arrays