Wikipedia:Verifiability

The threshold for inclusion in Wikipedia is verifiability, not truth. That is, whether readers can check that material in Wikipedia has already been published by a reliable source, not whether editors think it is true.
To show that it is not original research, all material in Wikipedia articles must be attributable to a reliable published source. But in practice not everything need actually be attributed. This policy requires that all quotations and any material challenged or likely to be challenged be attributed to a reliable, published source in the form of an inline citation, and that the source directly support the material in question.[1]
This policy is strictly applied to all material in the mainspace—articles, lists, sections of articles, and captions—without exception, and in particular to material about living persons. Anything that requires but lacks a source may be removed, and unsourced contentious material about living persons must be removed immediately. For how to write citations, see Citing sources

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