In mathematics, a symmetric matrix M {\displaystyle M} with real entries is positive-definite if the real number z T M z {\displaystyle z^{\operatorname {T} }Mz} is positive for every nonzero real column vector z, {\displaystyle z,} where z T {\displaystyle z^{\operatorname {T} }} is the transpose of z {\displaystyle z}. Wikipedia