Wikipedia:Dictionaries as sources

This is an essay on the Wikipedia:No original research § Primary, secondary and tertiary source policy. It contains the advice or opinions of one or more Wikipedia contributors. This page is not an encyclopedia article, nor is it one of Wikipedia's policies or guidelines, as it has not been thoroughly vetted by the community. Some essays represent widespread norms; others only represent minority viewpoints.

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This page in a nutshell: Dictionaries and glossaries present special challenges and limitations.

Wikipedia generally prefers secondary sources in support of articles. It has a policy distinguishing among primary, secondary, and tertiary sources. Dictionaries and glossaries present a special challenge in determining whether the source is primary, secondary, or tertiary. One dictionary or glossary may be considered a primary source among linguists, whereas for Wikipedia's purposes it is a secondary source. Another dictionary or glossary that among linguists is considered derivative, and thus secondary, is likely considered a tertiary source for Wikipedia's purposes. Additionally, some glossaries are considered primary sources for Wikipedia's purposes.

Dictionaries have limits to their utility. In general, the earliest known usage of a word cannot be definitively determined using a dictionary alone, and the same is true of stylings, such as hyphenated or open formats. Additionally, definitions are separate from etymologies; to use a centuries-old etymology as a modern definition is a mistake, and while dictionary definitions are usually reasonably precise, they are not necessarily mathematically precise for every word.