| Keyword | Function | Description | Parameters |
| Correlation matrices | |||
| ID | id() | Identity | 0 |
| AR1 | ar1() | First order autoregressive | 1 |
| AR2 | ar2() | Autoregressive | 2 |
| AR3 | ar3() | Autoregressive | 3 |
| SAR | sar() | Symmetric autoregressive | 1 |
| SAR2 | sar2() | Symmetric autoregressive | 2 |
| MA, MA1 | ma1() | Moving Average | 1 |
| MA2 | ma2() | Moving Average | 2 |
| ARMA | arma() | Autoregressive Moving Average | 2 |
| CORU | coru() | Uniform Correlation | 1 |
| CORB | corb() | Banded Correlation | w-1 |
| CORG | corg() | General Correlation | w(w-1)/2 |
| EXP | exp() | Exponential | 1 |
| GAU | gau() | Gaussian | 1 |
| IEXP | iexp() | Isotropic Exponential | 1 |
| IGAU | igau() | Isotropic Gaussian | 1 |
| IEUC | ieuc() | Isotrophic Euclidean | 1 |
| LVR | lvr() | Linear Variance | 1 |
| SPH | sph() | Spherical | 1 |
| CIR | cir() | Circular | 1 |
| AEXP | aexp() | Anisotropic Exponential | 2 |
| AGAU | agau() | Anisotropic Gaussian | 2 |
| MATk | matk() | Matern | k |
| Variance structures | |||
| DIAG | diag() | Diagonal | w |
| US | us() | Unstructured | w(w+1)/2 |
| OWNk | ownk() | User supplied matrix | k |
| ANTEk | antek() | Antedependence | w(w+1)/2 |
| CHOLk | cholk() | Cholesky - banded form | w(w+1)/2 |
| CHOLkC | cholkC() | Cholesky - column form | w(w+1)/2 |
| FAk | fak() | Factor Analytic (correlation form) | w(k+1) |
| FACVk | facvk() | Factor Analytic (covariance form) | w(k+1) |
| XFA k | xfak() | Extended Factor Analytic | w(k+1) |
| Fixed matrices | |||
| AINV | nrm() | Numerator Relationship matrix (A) | 0 or 1 |
| GIVk | grmk() | General (Inverse) Variance matrix | 0 or 1 |