Question

A square matrix that does not have an inverse is most specifically called a(n)

Answer 1

It's is called a singular.

Answer 2

A square matrix whose inverse is not defined is called a:

Singular Matrix.

Explanation:

Singular matrix--

A matrix is said to be singular if and only if it's determinant is zero.

Such a matrix does not have a matrix inverse.

Since, the inverse of a square matrix A is given by:

`A^(-1)=(1)/(|A|)\cdot (adj A)`

where
`A^(-1)` denote the inverse.

|A| denote the determinant of a matrix A.

(adj A) denote the adjoint matrix of A.

Now if the denominator i.e. |A| is zero then the term
`A^(-1)` is not defined.