class

Class is a term with multiple meanings across disciplines, and its precise sense depends on context. In sociology and anthropology, class refers to a system of ordering society based on economic resources, occupation, education, and prestige. Social classes influence life chances, access to goods, and social mobility, though thresholds and meanings vary by culture and era.

In biology, class is a taxonomic rank used in the classification of organisms. It sits below phylum and above order and groups organisms that share broad anatomical and developmental traits. Examples include Mammalia (mammals) and Aves (birds). Taxonomic classification evolves with new scientific evidence and methods.

In education, a class can mean a group of students who meet to learn together or a course or lesson unit. Class size, scheduling, and instructional design affect teaching and learning outcomes.

In computer science, a class is a blueprint for creating objects. It defines data fields (attributes) and procedures (methods) that operate on those data. Objects are instances of a class. Classes support concepts such as encapsulation, inheritance, and polymorphism, which are central to object-oriented programming.

In statistics and machine learning, a class is a category that instances may belong to. Classification tasks assign data to classes, such as spam versus legitimate email or multiple classes in multiclass problems. Performance is often measured with metrics derived from confusion matrices.

In set theory and logic, a class is a collection defined by a property. Some classes are too large to be sets (proper classes) and require careful formal treatment.