https://en.wikipedia.org/wiki/Invertible_matrix
A square matrix that is not invertible is called singular or degenerate. A square matrix is singular if and only if its determinant is 0. Singular matrices are rare in the sense that a square matrix randomly selected from a continuous uniform distribution on its entries will almost never be singular.
https://zh.wikipedia.org/wiki/逆矩阵
非奇异方阵或可逆方阵
https://zh.wikipedia.org/wiki/广义逆阵
