labelled

Labelled is the past participle and adjective form of the verb label, used primarily in British English. American English normally uses labeled. It denotes that something has been given a label or carries a label. As a noun, a label is a tag or descriptor attached to an object or piece of data.

In data science and machine learning, a labelled dataset is one in which each instance has an associated target value or category. Such datasets are used for supervised learning, enabling algorithms to learn mappings from input features to outputs. Labels can be categorical (class names) or numerical (regression targets), and the quality of labeling directly affects model performance.

In mathematics and computer science, labelled concepts describe structures with additional identifying information attached to components. A labelled graph assigns labels to vertices or edges from a specified set, rather than treating them as unlabeled connections. A labelled transition system uses action labels on transitions to represent possible state changes, aiding formal analysis of behavior.

In everyday use, labelled objects carry explicit information about origin, contents, warning statements, or other descriptors provided by a label. This sense is common in manufacturing, packaging, and documentation, where labeling helps identify and inform users.

Spelling conventions vary by region: labelled in most of the Commonwealth, labeled in the United States. The term remains widely used to indicate that labels have been applied or specified to attributes, data, or components.