Binary or binomial classification is the task of classifying the elements of a given set into two groups on the basis of a classification rule. Some typical binary classification tasks are:

• medical testing to determine if a patient has certain disease or not – the classification property is the presence of the disease;
• A "pass or fail" test method or quality control in factories; i.e. deciding if a specification has or has not been met: a Go/no go classification.
• An item may have a qualitative property; it does or does not have a specified characteristic
• information retrieval, namely deciding whether a page or an article should be in the result set of a search or not – the classification property is the relevance of the article, or the usefulness to the user.