Wikipedia:Defining

This is an information page. It is not a Wikipedia policy or guideline; rather, its purpose is to explain certain aspects of Wikipedia's norms or practices. It may reflect varying levels of consensus.

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This page explains how to apply the concept of defining characteristics in the context of Wikipedia categorization, by quoting the relevant guidance in several related guidelines.

Defining characteristics of an article's topic are central to categorizing the article. A defining characteristic is one that reliable sources commonly and consistently refer to^[1] in describing the topic, such as the nationality of a person or the geographic location of a place.

• • Articles should normally be included in the categories that are most closely related to the subject's defining characteristics.

    For example, Italian and artist are defining characteristics of Caravaggio, because virtually all reliable sources on the topic mention them, so that article is included in categories such as Category:Italian Baroque painters.

  • Categories should not group subjects by trivial characteristics that have little relevance to the topics, unless it can be shown that such a characteristic or grouping is notable.

    For example, Category:Italian people with dark eyebrows would likely be trivia, even if it's true, so the category does not exist, and Caravaggio is not in it.

  • For characteristics that are neither defining nor trivial, editors should use their judgment to choose which additional categories (if any) to include.

    For example, Caravaggio is included in the non-defining category of Category:Deaths from sepsis.

Biographical articles should be categorized by defining characteristics. As a rule of thumb for main biographies this includes the reason(s) for the person's notability; i.e., the characteristics the person is best known for. The principle of "defining characteristics" applies to categorizing people, as it does to any other categorization. As the guideline on categorization says:

Defining characteristics of an article's topic are central to categorizing the article. A defining characteristic is one that reliable sources commonly and consistently refer to^[2] in describing the topic, such as the nationality of a person or the geographic location of a place.

• For example, a film actor who holds a law degree should be categorized as a film actor, but not as a lawyer unless their legal career was notable in its own right or relevant to their acting career. Many people had assorted jobs before taking the one that made them notable; those other jobs should not be categorized. Similarly, celebrities commercializing a fragrance should not be in the perfumers category; not everything a celebrity does after becoming famous warrants categorization.

One of the central goals of the categorization system is to categorize articles by their defining characteristics. It is sometimes difficult to know whether or not a particular characteristic is "defining" for any given topic, and there is no one definition that can apply to all situations. However, the following suggestions or rules-of-thumb may be helpful:

• a defining characteristic is one that reliable, secondary sources commonly and consistently define, in prose, the subject as having. For example: "Subject is an adjective noun ..." or "Subject, an adjective noun, ...". If such examples are common, each of adjective and noun may be deemed to be "defining" for subject.
• if the characteristic would not be appropriate to mention in the lead section of an article (regardless of whether it is currently mentioned in the lead), it is probably not defining;
• if the characteristic falls within any of the forms of overcategorization mentioned on this page, it is probably not defining.

Often, users can become confused between the standards of notability, verifiability, and "definingness". Notability is the test that is used to determine whether a topic should have its own article. This test, combined with the test of verifiability, is used to determine whether particular information should be included in an article about a topic. Definingness is the test that is used to determine whether a category should be created for a particular attribute of a topic. In general, it is much easier to verifiably demonstrate that a particular characteristic is notable than to prove that it is a defining characteristic of the topic. In cases where a particular attribute about a topic is verifiable and notable but not defining, or where doubt exists, creation of a list is often the preferred alternative.

It is recommended to name or rename categories to have as little vagueness as possible, discouraging non-defining articles from being added. If you have just invented a subcategory on the spot that lacks a main article, it may not be a defining attribute. Examples include:

• Medical doctors instead of Medically-skilled people
• Quadcopters instead of Fast-moving drones
• Fiction about robots instead of Robots in fiction

In disputed cases, the categories for discussion process may be used to determine whether a particular characteristic is defining or not.

For example, there is consensus that places should not be categorized as established in the year of the earliest surviving historical record of the place.

• Wikipedia:Categorization/Ethnicity, gender, religion and sexuality § General #6