Dendrogram derives from two ancient greek words:
δένδρον (déndron), meaning "tree"
γράμμα(grámma), meaning "drawing, diagram"

Definition

A dendrogram is a diagram representing a tree.
It is a graphical visualization, a representation diagram used in different contexts.
It deploys an algorithm for cluster analysis.

In a network, the formation of clusters is defined as linked nodes, measured by the 
clustering coefficient in statistics and data mining.

This approach & technique can be used for classification or categorization of
subject matters in any domain whereby a node can be defined as an object or a phenomenon.

In hierarchical clustering, it illustrates the arrangement of the clusters
produced by the corresponding analyses.

In computational biology, it presents the clustering of genes or samples.

In phylogenetics, it displays the evolutionary relationships among various biological taxa.
As such, the dendrogram is also referred to as a phylogenetic tree

In Lin Hsin Hsin Art Museum
it is used for classification of art genres by:

Non-digital Art -- 2D
Non-digital Art -- 3D
Digital Art -- 2D
Digital Art -- 3D
Subject Matters