Introduction
In considering what is Wikipedia, one must recognize that the platform most people know — the text-based reference pages that appear in search results across the globe — occupies just one node in a constellation of collaborative knowledge efforts. Wikipedia is described in official terms as a free encyclopedia and an online encyclopedia operated by volunteers around the world. It is one of several initiatives supported by the Wikimedia Foundation, a non-profit organization based in the United States that “supports hundreds of thousands of people around the world in creating the largest free knowledge projects in history” and manages Wikipedia alongside other projects. (wikimediafoundation.org)
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This article presents a Wikipedia overview that situates Wikipedia among its “sister projects” — the related services and wiki sites run under the Wikimedia umbrella. It traces the organizational logic of these sister projects, clarifies their purpose and scope, and offers insight into patterns of use, participation, and the broader systemic architecture of Wikimedia’s collaborative knowledge ecosystem.
Wikimedia’s Organizational Framework
The Wikimedia Foundation’s mission centers on producing and disseminating content that is freely accessible and collaboratively developed. Wikipedia itself is the most familiar manifestation of this mission; its growth and reach have shaped public expectations about what an encyclopedia can be in an age of digital connectivity. Yet Wikipedia is but one component of a broader family of platforms, each structured as a wiki site and governed by similar principles of openness, volunteer contribution, and Creative Commons or free licensing. (wikimediafoundation.org)
A Wikipedia introduction necessarily begins with that context: Wikipedia is one of multiple projects that share the same underlying software (MediaWiki) and are integrated into a shared volunteer-driven infrastructure. These projects collectively serve varied informational needs — from dictionaries and source texts to multimedia repositories and educational tools. (wikimediafoundation.org)
The term “sister projects” is used internally and by observers to designate the initiatives closely affiliated with Wikipedia, all of which are developed collaboratively via wikis. These projects form a network that operates parallel to, and in conjunction with, Wikipedia itself. (en.wikipedia.org)
Core Reference Projects
In addition to Wikipedia, the Wikimedia portfolio includes several projects centered on reference materials. Each is intended to cover a distinct type of content or format, organized and maintained by volunteer communities.
Wiktionary
The project known as Wiktionary is “a multilingual, web-based project to create a free content dictionary of terms … in a large number of natural languages” that includes definitions, etymologies, pronunciations, and translations. Its architecture mirrors Wikipedia’s wiki model but with a lexicographical focus. (en.wikipedia.org)
As of early 2026, Wiktionary has editions in numerous languages, with millions of lexical entries that enrich projects across Wikimedia by supplying definitional data, synonyms, and usage notes — a resource used in natural language research tasks as well as general reference work. (en.wikipedia.org)
Wikiquote
Wikiquote is dedicated to the collection of sourced quotations from individuals, literary works, speeches, films, and other cultural artifacts. First launched in 2003, the project has expanded into multiple languages and cross-links to Wikipedia articles when relevant. (en.wikipedia.org)
This project carries a specialized mandate: by organizing quotes according to subject or author, it complements Wikipedia’s biographical and topical articles with curated primary source material. Its editorial culture prioritizes accurate sourcing and provenance, a principle that aligns with the norms of citation that govern Wikipedia as a free encyclopedia. (en.wikipedia.org)
Wikibooks
Wikibooks is a repository for open-content textbooks, instructional guides, and annotated texts. It aims to produce “free e-book resources including textbooks, annotated texts, instructional guides, and manuals” that are freely licensed and editable, thus serving educational communities and learners seeking resources they can adapt to their needs. (wikimediafoundation.org)
Wikibooks’ structure resembles Wikipedia’s but with a narrative logic oriented toward structured learning sequences rather than general reference. Contributors build modules, sections, and books that can function as self-study resources or classroom supplements.
Wikisource
Wikisource describes itself as a “free library” of source texts — a project that houses historical documents, original writings, constitutions, and public domain works in a searchable digital environment. (wikimediafoundation.org)
Unlike Wikipedia’s articles, which are secondary accounts synthesizing knowledge, the materials on Wikisource are themselves primary objects: legal texts, historic speeches, classical literature, and other works that require careful transcription and validation against authoritative originals. (wikimediafoundation.org)
Collections and Media Projects
Wikimedia Commons
Wikimedia Commons serves as a media repository where volunteers upload and categorize multimedia files — images, audio recordings, and videos — that can be reused across Wikimedia projects. This repository underpins the multimedia content found throughout Wikipedia and other platforms. (wikimediafoundation.org)
The Commons repository is distinguished by its emphasis on freely licensed or public-domain material that can be used without cost, provided licensing terms are respected. Its files are used not only within Wikimedia projects but also by educators, journalists, researchers, and digital creators seeking high-quality media with liberal reuse terms. (information-services.ed.ac.uk)
Wikispecies
Wikispecies is an initiative geared toward scientific communities: a taxonomic directory designed to catalog the diversity of biological life. It is “a wiki-based online project for Linnaean taxonomy” that organizes species data structured around scientific classification. (en.wikipedia.org)
The project is particularly notable for its growth trajectory: by early 2025, Wikispecies had exceeded 900,000 article pages, many of which contain detailed classification data linked to Wikipedia entries. (en.wikipedia.org)
Educational and News Platforms
Wikiversity
Wikiversity stands apart from Wikipedia by emphasizing learning communities and educational materials rather than encyclopedic articles. Its mission is to support study programs, tutorials, and research activities across subjects and levels. (en.wikipedia.org)
This project supports initiatives like WikiJournals, peer-reviewed open access publications that can be cited in academic work, a feature that differentiates it from many other Wikimedia projects. (en.wikipedia.org)
Wikinews
Wikinews is a participatory journalism project that offers a space for collaborative reporting on current events. Members of the community write articles that adhere to a fact-checking process and are reviewed for neutrality. While it does not command the scale of major commercial news outlets, it represents an effort to apply wiki principles to news production. (libguides.lmu.edu)
Wikivoyage
Although less widely recognized than Wikipedia, Wikivoyage is a collaborative travel guide project that crowdsources travel information and advice. As with other sister projects, the content is user-generated and editable, with a focus on practical travel content rather than general reference articles. (wikimediafoundation.org)
Data and Infrastructure Projects
Wikidata
Wikidata acts as a shared structured data repository that other Wikimedia projects draw upon. It stores data in machine-readable form — facts about people, places, dates, and categories — that Wikipedia and its siblings can reference programmatically. (wikidata.org)
This centralization of structured knowledge supports consistency and improves searchability across platforms, linking disparate articles through common identifiers.
Meta-Wiki
Meta-Wiki is differentiated from the content projects. It is a coordination hub where contributors engage in multilingual discussion, propose initiatives that affect multiple Wikimedia projects, and participate in governance or planning tasks. (meta.wikimedia.org)
Patterns of Collaboration and Shared Infrastructure
Across the Wikimedia ecosystem, all sister projects operate on shared wiki basics such as open editing, version histories, talk pages, and volunteer governance. They rely on the same software platform — MediaWiki — which facilitates revisions, user accounts, and content management. (en.wikibooks.org)
The interconnectedness of these projects is significant. Content created on one project can link to or enrich another. A taxonomic entry in Wikispecies may link to a detailed Wikipedia article; an image uploaded to Wikimedia Commons can illustrate an encyclopedic entry; a term defined in Wiktionary can be referenced in Wikipedia articles or educational texts in Wikibooks. This interoperable architecture is central to how Wikimedia operates as a network of knowledge rather than isolated platforms.
Final Considerations
An accurate Wikipedia definition must encompass both the encyclopedia itself and its network of related projects. The Wikimedia sister projects operate as an ecosystem of collaborative platforms — all structured as wiki sites — each with specific content domains and editorial cultures. These projects uphold shared values of free access, openness to contribution, and collaborative development.
The broader Wikimedia infrastructure supports a range of formats — encyclopedic articles, dictionaries, quotations, textbooks, source texts, media libraries, taxonomic catalogues, structured databases, and participatory journalism. Collective participation in these projects is voluntary, global, and driven by community norms that emphasize verifiability, transparency, and neutrality.
Understanding this network offers a clearer perspective on about Wikipedia not just as a single reference work, but as part of a larger project of open knowledge. The diversity of sister projects reflects the varied ways in which people seek, create, and maintain information. Whether through a dictionary in many languages, a compilation of sourced quotations, a library of media files, or structured datasets for research, these platforms illustrate that collaborative, open-access information can be specialized, interconnected, and multidimensional — even beyond the boundaries of a traditional online encyclopedia.
