The graph below shows two clusters of points $($defined by the circles$)$ of three points each. There are different methods for measuring the distance between the two clusters. Single linkage$--$the distance between the two closest points from each cluster. Complete linkage$--$the distance between the two most distant points from each cluster. Group Average Linkage$--$the average of all the distances between points in different clusters. Centroid Linkage$-$the distance between the centroid or average point $($denoted by a central dot in each cluster below$)$ between clusters. Click on the graph to cycle through illustrations of each linkage definition and the computed distances.