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On Wikipedia, relevance is simply whether a fact in an article is useful to the reader and is within the scope of the article. If a fact is not relevant to the topic of the article, it should not be mentioned in that article. This does not mean it can not be mentioned in some other article. Mentioning things that are irrelevant to an article's topic can unnecessarily bloat an article, making it difficult for a reader to remain focused, and can also give the things mentioned undue weight.