Clustering aims at finding groups in data. “Cluster” is an intuitive concept and does
not have a mathematically rigorous definition. The members of one cluster should be
similar to one another and dissimilar to the members of other clusters. A clustering
algorithm operates on an unlabeled data set Z and produces a partition on it.
For Classes and Class Labels,
class contains similar objects, whereas objects from different classes
are dissimilar. Some classes have a clear-cut meaning, and in the simplest case
are mutually exclusive. For example, in signature verification, the signature is either
genuine or forged. The true class is one of the two, no matter that we might not be
able to guess correctly from the observation of a particular signature.