[2] It is a common source of open data that Wikimedia projects such as Wikipedia,[3][4] and anyone else, is able to use under the CC0 public domain license.

Wikidata is a wiki powered by the software MediaWiki, including its extension for semi-structured data, the Wikibase.

[5] Wikidata is a document-oriented database, focusing on items, which represent any kind of topic, concept, or object.

Each item is allocated a unique, persistent identifier, a positive integer prefixed with the upper-case letter Q, known as a "QID".

[6] This enables the basic information required to identify the topic that the item covers to be translated without favouring any language.

Examples of items include 1988 Summer Olympics (Q8470), love (Q316), Johnny Cash (Q42775), Elvis Presley (Q303), and Gorilla (Q36611).

Formally, they consist of key–value pairs, which match a property (such as "author", or "publication date") with one or more entity values (such as "Sir Arthur Conan Doyle" or "1902").

Each property has a numeric identifier prefixed with a capital P and a page on Wikidata with optional label, description, aliases, and statements.

[14][15] Similarly, Wikidata's lexemes are items with a structure that makes them more suitable to store lexicographical data.

This extension has since been installed on Wikidata[25] and enables contributors to use ShEx for validating and describing Resource Description Framework data in items and lexemes.

Any item or lexeme on Wikidata can be validated against an entity schema,[clarification needed] and this makes it an important tool for quality assurance.

Wikidata's content collections include data for biographies,[26] medicine,[27] digital humanities,[28] scholarly metadata through the WikiCite project.

[30] The creation of the project was funded by donations from the Allen Institute for Artificial Intelligence, the Gordon and Betty Moore Foundation, and Google, Inc., totaling €1.3 million.

[36] Wikipedia language editions were still not able to access Wikidata, so they needed to continue to maintain their own lists of interlanguage links.

[44] The ability for the various language editions of Wikipedia to access data from Wikidata was rolled out progressively between 27 March and 25 April 2013.

[59] As of November 2018[update], Wikidata information was used in 58.4% of all English Wikipedia articles, mostly for external identifiers or coordinate locations.

In aggregate, data from Wikidata is shown in 64% of all Wikipedias' pages, 93% of all Wikivoyage articles, 34% of all Wikiquotes', 32% of all Wikisources', and 27% of Wikimedia Commons.