Cluster

A cluster is a group of similar things that are located close to one another or are linked in some functional way. The term is used in various disciplines to denote aggregation, from natural phenomena to man-made systems. In statistics and data analysis, cluster analysis aims to partition a set of objects into groups, or clusters, so that members of the same cluster are more similar to each other than to members of different clusters.

In computing, a cluster refers to a set of connected computers or servers that work together to provide combined resources, redundancy, and resilience. Clustered systems are used for high availability, load balancing, and parallel processing. In cloud and grid computing, clusters can scale by adding more nodes.

In astronomy, star clusters are loose associations of stars bound by gravity. Open clusters are relatively young and contain hundreds to thousands of stars, while globular clusters are dense, ancient assemblies of tens of thousands to millions of stars orbiting galaxies.

In biology and medicine, clusters can describe groups of cells, organisms, or disease cases that occur in proximity in space or time. The term is used in epidemiology to denote outbreaks that are not randomly distributed. In linguistics and phonology, a consonant cluster is a group of two or more consonants occurring together in a syllable.

The word also appears in business and geography to describe clusters of firms or urban districts. As a general concept, clustering emphasizes association and proximity as defining features.