This glossary defines important Wikidata concepts and refers to more detailed information. See Wikidata:Introduction for a general introduction into Wikidata and the glossary guidelines for how to write and improve glossary entries.
|Alias (also also known as) is an alternative name for an item or property. The usual or most important name is the label. Aliases help people to find an item even if they don’t search with the label. For example, the item Q2 has the label “Earth” and aliases such as “Tellus” and “Blue Planet”.
|Badges are optional markers that can be attached to a sitelink. For instance a sitelink can be marked to link to a "featured article" and/or to a "proofread" page.
|Claim is a piece of data about the entity on whose page the claim appears. A claim consists of a property (such as "Location") and either a value (e.g., "Germany") or one of the special cases "no value" and "unknown value". A claim can have qualifiers, such as temporal qualifiers saying that the claim is valid within a specific time frame. Compared to triples in the RDF data model, a claim uses a property to express the predicate of a triplet and a value to express the object of a triplet. Claims form part of statements on item pages, where they can be augmented with references and ranks; they can also occur on non-item data pages.|
|Constraint is a rule how a particular property should be used. For instance each instance human should only have one date of birth (P569), so there is a single value constraint on this property.
|Datatype (data value type or value type) is the kind of data values that may be assigned to a property, and specifies how the data values are stored in each claim. Each property is assigned a pre-defined datatype. Not all values can be linked, as long as there are certain datatypes missing. The development of new datatypes is still in progress. See also Special:ListDatatypes for currently available datatypes.
► Help:Data type
|Description is a language-specific descriptive phrase for an item, property or query. It provides context for the label (for example, there are many items about places with the label "Cambridge"). The description therefore does not need to be unique, neither within a language or Wikidata in general, but it must be unique together with the label. Uniqueness for a combination of a label and a description is a hard constraint. If your contribution does not meet this requirement you cannot save the change.
|Entity is the content of a Wikidata page, that either may be an item (in the main namespace), a property (in the property namespace). Every entity is uniquely identified by an entity ID, which is a prefixed number, for example starting with the prefix
|External identifier Some properties have values that are strings used in the databases of external organisations. They uniquely identify an item. For example, an ISBN for a book or the unique part of the URL of a movie or an actor in the Internet Movie Database.|
|Item refers to a real-world object, concept, or event that is given an identifier (an equivalent of a name) in Wikidata together with information about it. Each item has a corresponding Wikipage in the Wikidata main namespace. Items are identified by a prefixed id (like Q5), or by a sitelink to an external page, or by a unique combination of multilingual label and description. Items may also have aliases to ease lookup. The main data part of an item is the list of statements about the item. An item can be viewed as the subject-part of a triplet in linked data.
|Label (also name) is the main name given to identify an entity (i.e. an item or a property). E.g.: the item with the item identifier Q7378 has the English label “elephant”. Every entity has exactly one label in a given human language. Labels do not need to be unique. Descriptions and aliases are used to distinguish between entities with the same label. Wikidata pages do not have labels, but titles.
|Language attributes are the language-specific labels, aliases and descriptions that are assigned to items, properties and queries. These are human-readable text to improve understanding of the scope of the item; for example the specific type of real world entity. If they are missing some of them can be replaced by strings from alternate languages, following the language fallback chains.|
|Language fallbacks (also language chains) are methods to systematically replace missing language attributes with strings from alternate languages. The exact replacement rules can be chosen depending on the type of page, whether the user is logged in, or the user preferred languages.|
|Mainspace is one of the namespaces in a wiki. Other than other namespaces, it does not have a prefix. In Wikidata, the mainspace contains the pages with the items.|
|MediaWiki is the software that runs Wikidata, Wikipedia and other wikis. The MediaWiki installation of Wikidata makes use of the Wikibase extension.
► What is MediaWiki
|Meta pages These are all pages that are not entities, i.e. do not belong to the data namespaces. Wikidata meta pages contain unstructured content represented by conventional MediaWiki code, and perhaps also future Wikidata client side inclusion code. Examples are talk pages, category pages, project pages (in the Wikidata namespace) and help pages (in the help namespace). Meta pages also comprise content and data automatically generated by the MediaWiki software (for example, the edit history of a page, or special pages).|
|Namespaces are a kind of category for pages in a wiki. Per namespace you may have different rules about the pages and their content. In Wikidata, the most important namespace (or ‘main namespace’) is for the Wikidata items. The URL of such a page ends on a
|Page An internal or external webpage with a unique title, for example an article in Wikipedia main namespace or an item in Wikidata main namespace. In Wikidata, the term "page" may refer to an item or a property page in the data namespaces, a meta page in other namespaces or an external linked page on Wikipedia or other Wikimedia site or an other external site, that is referenced using a sitelink. Pages in the main namespace of Wikidata are about items, and one page can only hold one item.|
|Project is a term often used in the Wikimedia movement. In most cases, people mean a Wikimedia Wiki. So in Wikidata, the term usually refers to Wikidata itself.|
|Property (also attribute) is the descriptor for a data value, or some other relation or composite or possibly missing value, but not the data value or values themselves. Each statement at an item page links to a property, and assigns the property one or several values, or some other relation or composite or possibly missing value. The property is stored on a page in the Property namespace, and includes a declaration of the datatype for the property values. Compared to linked data, the property represents a triplet's predicate.
|Qualifier is a part of the claim that says something about the specific claim, often in a descriptive way. A qualifier might be a term according to a specific vocabulary but can also be a variant descriptive phrase (whether those terms or phrases are free text or part of some vocabulary would probably be up to the Wikidata community).
|Query is a search across items in Wikidata. By now queries can be executed in the SPARQL query language. It is planned to extent Wikidata by queries as entities defined on their own pages.
► Wikidata:SPARQL query service
|Rank is a quality factor used for simple selection/filtering in cases where there are many statements for a given property. In such cases, you may want to indicate which statement is more important or relevant than other statements. By default, a statement has the rank "normal", but you can change this to either "preferred" or "deprecated".
|Reference (or source) describes the origin of a statement in Wikidata. A reference is often an item in its own right; for example, a book. Wikidata does not aim to answer the question of whether a statement is correct, but merely whether the statement appears in a reference.
|Site is a reference to an external website in general, but in sitelinks it refers to specific registered wikis, for example a Wikipedia language version. Those sites are referenced by global site identifiers or for short siteid, technically corresponding to the wiki's DBname. For example the Latin Wikipedia's siteid is
|Sitelink (Interlanguage link) is an identification of a linked page on another site. It consists of a site identifier and a title, and are stored in individual items in Wikidata. They are used both for identifying an item from an external site, and as a central storage of interwiki (interlanguage) links.
|Snak is a technical term of Wikibase software which data users are most likely to encounter when accessing Wikidata through the MediaWiki API. It refers to the combination of a property and either a value or one of the special cases "no value" and "unknown value". Snaks can be found in claims and in qualifiers as part of statements. The "main snak" is the most important part of the statement, e.g., in the statement "Emma Watson was a cast member of Harry Potter and the Philosopher's Stone in the role of Hermione Granger" it refers to the part "Emma Watson was a cast member of Harry Potter and the Philosopher's Stone".|
|Statement is a piece of data about an item, recorded on the item's page. A statement consists of a claim (a property-value pair such as "Location: Germany", together with optional qualifiers), augmented by optional references (giving the source for the claim) and an optional rank (used to distinguish between several claims containing the same property). Wikidata makes no assumptions about the correctness of statements, but merely collects and reports them with a reference to a source.
|String (also character string) is a general term for a sequence of freely chosen characters interpreted as text (e.g. "Hello") — as opposed to a value interpreted as a numerical value (3.14), a link to an item (e.g.
|Title is the name of a page. The title is unique per wiki. In Wikidata a title is either an item identifier such as Q42 or it starts with a namespace prefix such as
|Values (also datavalues) are the information pieces embedded in each claim. Depending on their datatype, they can be a single value (like a number) or a value consisting of several parts (like a geographical position with longitude and latitude). The special cases "unknown value" or "no value" can also be selected.
|Wikibase is the software behind Wikidata. It consists of a set of extensions to the MediaWiki software. Thanks to these extentions, Wikidata can manage data in items and properties, and query and display this data.
|Wikidata is a Wikimedia project that runs an instance of MediaWiki with the Wikibase extensions. It enables Wikidata editors to enter data and browse pages.
|Wikimedia is the name of a movement which consists of people and organizations. Wikidata is run by the Wikimedia Foundation together with other wikis such as Wikipedia. The Wikibase software is mainly developed by Wikimedia Germany which is one of the national Wikimedia affiliations.
|Wiki is a concept for a website. Wikipedia and Wikidata are wikis. A wiki in general is a website that can be edited by the visitors.