Classification, also known as typification or systematology, is a systematic collection of abstract classes (otherwise called concepts, types or categories) used for demarcation and organisational purposes.

The individual classes are usually specified using classification – by dividing up objects based on specific characteristics. Many classifications are organised into hierarchical layers with varying levels of differentiation. The sum of the class names forms a controlled vocabulary. The classification of an object by selecting a suitable class for the given classification is known as classing or class assignation.