*2.2.1 Clustering*

Clustering is a way of organising items into clusters so that the items that share the most similarities stay in one group and share little to none with the objects in another group. The data items are classified based on the existence or lack of commonalities discovered during the cluster analysis.

## *2.2.2 Association*

A rule of association is used to uncover links between variables in a sizable database using unsupervised learning techniques. It establishes the group of items that cooccur in the collection. Marketing strategy is more effective because to the association rule. Those who purchase X (let us say, bread) also frequently buy Y (let us say, butter or jam). Market Basket Analysis is an illustration of an association rule in action.

Popular unsupervised learning algorithms are listed below:
