| Keyword | Description | Parameters |
| Correlation matrices | ||
| ID | Identity | 0 |
| AR1 | First order autoregressive | 1 |
| AR2 | Autoregressive | 2 |
| AR3 | Autoregressive | 3 |
| SAR | Symmetric autoregressive | 1 |
| SAR2 | Symmetric autoregressive | 2 |
| MA, MA1 | Moving Average | 1 |
| MA2 | Moving Average | 2 |
| ARMA | Autoregressive Moving Average | 2 |
| CORU | Uniform Correlation | 1 |
| CORB | Banded Correlation | w-1 |
| CORG | General Correlation | w(w-1)/2 |
| EXP | Exponential | 1 |
| GAU | Gaussian | 1 |
| IEXP | Isotropic Exponential | 1 |
| IGAU | Isotropic Gaussian | 1 |
| IEUC | Isotrophic Euclidean | 1 |
| LVR | Linear Variance | 1 |
| SPH | Spherical | 1 |
| CIR | Circular | 1 |
| AEXP | Anisotropic Exponential | 2 |
| AGAU | Anisotropic Gaussian | 2 |
| MATk | Matern | k |
| Variance structures | ||
| DIAG | Diagonal | w |
| US | Unstructured | w(w+1)/2 |
| OWNk | User supplied matrix | k |
| ANTEk | Antedependence | w(w+1)/2 |
| CHOLk | Cholesky - banded form | w(w+1)/2 |
| CHOLkC | Cholesky - column form | w(w+1)/2 |
| FAk | Factor Analytic (correlation form) | w(k+1) |
| FACV | Factor Analytic (covariance form) | w(k+1) |
| XFA k | Extended Factor Analytic | w(k+1) |
| Fixed matrices | ||
| AINV | Numerator Relationship matrix (A) | 0 or 1 |
| GIVk | User supplied General (Inverse) Variance matrix | 0 or 1 |