A Cladogram, in context of genetic genealogy, is a borrowed term from biology that mostly applies to its use here.

A Cladogram, in its purest definition, is simply a diagram that shows relations between organisms. Key is, unlike a phylogenetic tree, it is unordered in time and not necessarily rooted. When applied to STR analysis, cladograms are diagrams showing changes in individual markers from a likely common root. This common root, which itself is calculated by looking at all the samples provided, is called the modal and defined as the likely value set of some unidentified MRCA.

Unlike cladograms in biology, and more similar to phylogenetic trees, an order to the changes is being implied. Like Phylogenetic Trees, cladograms in this context are rooted. The more test samples to compare, the better the structure to the resultant diagram. The diagram creation assumes that markers have not changed back from their modal determined value; which is not always the case. If too many unrelated test results are analyzed, a root and modal may not be determined.

Cladograms are associated with STR testing in genetic genealogy whereas Phylogenetic Trees are associated with SNP testing and Haplogroups.