Each dyad in a directed graph may be in one of four states: the null state (\(a \not\leftrightarrow b\)), the complete or mutual state (\(a \leftrightarrow b\)), and either of two asymmetric states (\(a \leftarrow b\) or \(a \rightarrow b\)). Holland and Leinhardt's dyad census classifies each dyad into the mutual, asymmetric, or null categories, counting the number of each within the digraph. These counts can be used as the basis for null hypothesis tests (since their distributions are known under assumptions such as constant edge probability), or for the generation of random graphs (e.g., via the U|MAN distribution, which conditions on the numbers of mutual, asymmetric, and null dyads in each graph).