Wikipedia:No original research

Wikipedia does not publish original research. The term "original research" refers to material—such as facts, allegations, ideas, and stories—not already published by reliable sources. It also refers to any analysis or synthesis of published material to advance a position not advanced by the sources.
This means that all material added to articles must be attributable to a reliable published source, even if not actually attributed. The sourcing policy, Verifiability, says a source must be provided for all quotations, and for anything challenged or likely to be challenged—but a source must exist even for material that is never challenged. "Paris is the capital of France" needs no source because no one is likely to object to it, but we know that sources for that sentence exist. If no source exists for something you want to add to Wikipedia, it is "original research". To demonstrate that you are not adding original research, you must be able to cite reliable published sources that are both directly related to the topic of the article, and that directly support the material as presented.

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