Mathematica (wolfram language) uses asterisk () for general multiplication (scalar x scalar or scalar x matrix). But use the dot (.) for matrix multiplication.

Mathematica (wolfram language) uses asterisk () for general multiplication (scalar x scalar or scalar x matrix). But use the dot (.) for matrix multiplication. So if you have defined A as constant (or scalar in general) and B is a matrix then AB will work A.B will give dimension error If both A and B is matrices then A.B will give you matrix multiplication. A*B will give you a element wise multiplication. This behavior is actually confusing first but if you work a lot with mathematics you will find it makes sense after sometime.