broadcasting

Expanding the shape of an operand in a matrix math operation to dimensions compatible for that operation. For example, linear algebra requires that the two operands in a matrix addition operation must have the same dimensions. Consequently, you can't add a matrix of shape (m, n) to a vector of length n. Broadcasting enables this operation by virtually expanding the vector of length n to a matrix of shape (m, n) by replicating the same values down each column.

Given the following definitions of A and B, linear algebra prohibits A+B because A and B have different dimensions:

However, broadcasting enables the operation A+B by virtually expanding B to:

--- See the following description of broadcasting in NumPy for more details.