A mathematical method for taking the square root of a symmetric matrix. The Cholesky root of a matrix A is L, where A = LL`, and L is a lower-triangular matrix. It is useful in Quantitative Trait Locus (QTL) analysis because it allows modeling of a Pedigree-induced Covariance structure via a Mixed Model. It more efficiently solves a kinship matrix (see K Matrix) compared to classical LU decomposition, thus improves execution time. However, it should not be applied to ill-conditioned matrices containing sparse or low-quality data.