Wikipedia:SYN

The prohibition against OR means that all material added to articles must be attributable to a reliable, published source, even if not actually attributed. The verifiability policy says that an inline citation to a reliable 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. For example: the statement "the capital of France is Paris" needs no source, because no one is likely to object to it and we know that sources exist for it. The statement is attributable, even if not attributed.

Despite the need to attribute content to reliable sources, you must not plagiarize them or violate their copyrights. Rewriting source material in your own words, while substantially retaining the meaning of the references, is not considered to be original research.

"No original research" (NOR) is one of three core content policies that, along with Neutral point of view and Verifiability, determines the type and quality of material acceptable in articles. Because these policies work in harmony, they should not be interpreted in isolation from one another, and editors should familiarize themselves with all three. For questions about whether any particular edit constitutes original research, see the NOR noticeboard.

Research that consists of collecting and organizing material from existing sources within the provisions of this and other content policies is fundamental to writing an encyclopedia. Best practice is to research the most reliable sources on the topic and summarize what they say in your own words, with each statement in the article attributable to a source that makes that statement explicitly. Source material should be carefully summarized or rephrased without changing its meaning or implication. Take care not to go beyond what is expressed in the sources, or to use them in ways inconsistent with the intention of the source, such as using material out of context. In short, stick to the sources.

Any material that is challenged or likely to be challenged must be supported by a reliable source. Material for which no reliable source can be found is considered original research. The only way you can show your edit is not original research is to cite a reliable published source that contains the same material. Even with well-sourced material, if you use it out of context, or to reach or imply a conclusion not directly and explicitly supported by the source, you are engaging in original research; see below.

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