A dendrogram is a tree diagram frequently used to illustrate the arrangement of the clusters produced by a clustering algorithm (see cluster analysis). Dendrograms are often used in computational biology to illustrate the clustering of genes.
Dendron is the Greek word for tree (Greek: tree, tree-like structure; trees).
The hierarchical clustering dendrogram would be as such:
Here the top row of nodes represent data, and the remaining nodes represent the clusters to which the data belong, and the arrows represent the distance.