Classification is a general process related to categorization, in which ideas and objects are recognized, differentiated, and understood. A classification system is an approach to accomplishing classification. In machine learning, classification is considered as an instance of supervised learning, i.e. learning where a training set of correctly identified observations are available. Whereas in statistics, classification is often done with logistic regression or a similar procedure, the properties of observations are termed explanatory variables, and the categories to be predicted are known as outcomes, which are considered to be possible values of the dependent variable.