Tag

A tag is a label assigned to an item to describe its content or attributes. Tags are used to organize, search, and discover information across digital and physical media. They can be user-generated or system-assigned and may rely on free-form keywords, controlled vocabularies, or ontologies.

In digital media, tagging allows content to be grouped by topics, moods, or characteristics. Hashtags on social networks function as tags that aggregate posts around a topic and support trends, campaigns, or communities. Tagging also underpins metadata schemes in content management systems and file storage, enabling filtering and taxonomies.

In computing and markup languages, a tag refers to a symbolic label that marks a piece of content. In HTML and XML, tags define elements and their structure. Tags come in opening and closing pairs and can carry attributes that modify their behavior or appearance.

In linguistics and natural language processing, tagging assigns labels to tokens, such as part-of-speech tags (noun, verb) or named-entity tags (person, organization, location), to enable parsing and information extraction.

Other uses include the social game of tag, in which players chase and touch others to transfer the it role; the verb to tag meaning to label something; and in software or version control, tagging creates a reference point in a history or repository.