Multiclass classification

Not to be confused with multi-label classification. Not to be confused with multi-label classification. In machine learning, multiclass or multinomial classification is the problem of classifying instances into one of three or more classes. (Classifying instances into one of two classes is called binary classification.) While some classification algorithms naturally permit the use of more than two classes, others are by nature binary algorithms; these can, however, be turned into multinomial classifiers by a variety of strategies. Multiclass classification should not be confused with multi-label classification, where multiple labels are to be predicted for each instance. The existing multi-class classification techniques can be categorized into (i) Transformation to binary (ii) Extension from binary and (iii) Hierarchical classification.