In
machine learning,
multi-label classification and the strongly related problem of
multi-output classification are variants of the
classification problem where multiple target labels must be assigned to each instance. Multi-label classification should not be confused with
multiclass classification, which is the problem of categorizing instances into one of more than two classes. Formally, multi-label learning can be phrased as the problem of finding a model that maps inputs
x to binary vectors
y, rather than scalar outputs as in the ordinary classification problem.