Maintaining a neutral point of view (NPOV) is one of the five pillars and founding principles of Wikipedia. This policy says that we accept all the significant viewpoints on an issue. Instead of simply stating one perspective, we try to present all relevant viewpoints without judging them. Our aim is to be informative, not persuasive. Our policy does NOT mean that our articles are expected to be 100% objective, since in any dispute all sides believe their view to be true.
Wikipedia does not achieve balance by giving all opposing points of view equal space or treating them as equally valid. Views should be represented in proportion to their representation in reliable sources. When the subject of the article is a fringe theory, such as HIV/AIDS denialism or Barack Obama citizenship conspiracy theories, the article should give much more weight to the mainstream view with the fringe view clearly described as such.
It is okay to state opinions in articles, but they must be presented as opinions, not as fact. It is a good idea to attribute these opinions, for example "Supporters of this say that..." or "Notable commentator X believes that..."
You might hear Wikipedians referring to an article as having a "POV" problem. This is Wikipedia slang for a biased article, or one obviously written from a single perspective. Articles that are written like advertising would fall in this category, as would a political diatribe. In a less extreme case, an article might have "POV" problems if it spends significantly more time discussing one view than another view of equivalent significance, even if each view is presented neutrally, or if the article gives excessive coverage to a minor viewpoint.
If you are going to spend time on controversial articles in subjects like religion or politics, it is important that you read the neutral point of view policy page as soon as possible. You should probably also read the essay Staying cool when the editing gets hot. If you are going to spend your time on less emotional topics such as math, or cooking, you should still read the policies, but it is a less pressing concern. Keep in mind the advice here, and read the full policy if an NPOV issue comes up.
Wikipedia requires verifiable content, which means that you may only write what reliable sources have said about topics. If you cannot find reliable sources to back up your information, it cannot be included even if you think it is "true". You must cite sources for any information you contribute that is controversial or likely to be challenged, preferably by adding a footnote, as discussed in the "Citing Sources" page of this tutorial. Citations help our readers to verify what you have written and to find more information.
"Paris is the capital of France" is an example of a statement that does not necessarily need to be sourced, because it's common knowledge and everybody knows that there are dozens of sources which could be cited. The information is attributable, even if it is not attributed.
If any websites would be of particular interest to a reader of an article, they should be listed and linked to in an "External links" section. Books of particular interest should be listed in a "Further reading" section, but only if they were not used as sources for the article.
Wikipedia is not the place for original research — that is, facts, allegations, or ideas for which no reliable, published sources exist. This includes any analysis or synthesis of published material that serves to advance a position not advanced by the sources. Sources must support material directly and in context. For example, the statement "most computer scientists believe that P ≠ NP" must be supported by a reliable source which says that most computer scientists believe this, not by five citations of computer scientists saying that they themselves believe this without claiming to speak for the majority.
To prevent adding original research, avoiddirectly using primary sources if possible; instead, use secondary or tertiary sources that interpret and synthesize primary sources. Do not interpret, infer from, summarize, or synthesize primary sources yourself.
Routine calculations, translations from other languages, and faithful transcriptions of published audio and video are generally not considered original research.
The Manual of Style documents Wikipedia's house style. Its goal is to make using Wikipedia easier and more intuitive by promoting clarity and cohesion while helping editors write articles with consistent and precise language, layout, and formatting. Style and formatting should be consistent within an article, though not necessarily throughout Wikipedia. Where more than one style is acceptable, editors should not change an article from one of those styles to another without a good reason.
Wikipedia encourages an atmosphere of friendliness and openness. Of course, in practice there are sometimes disagreements and even an occasional heated argument, but members of the community are expected to behave in a generally civil manner.
The most important thing to keep in mind is that you should always assume good faith on the part of other editors. Do not assume that someone is acting out of spite or malice. If someone does something that upsets you, leave a polite message on the relevant article's talk page or on the user's talk page, and ask why. You may find that you have avoided a misunderstanding and saved yourself some embarrassment.
Wikipedia is an editable encyclopedia (along with some topics that would typically be found in an almanac). Hence, articles should consist of encyclopedic information about "notable" subjects. What exactly constitutes notability is the subject of constant debate on Wikipedia, but in no case should there be (per Wikipedia rules) an article for every person on the planet, or for every company that sells anything, or for each street in every town in the world. However, there are sister projects for certain types of non-encyclopedic content.
Encyclopedia articles are primarily about the subject, not the words for the subject, so any article that simply defines and explains the usages of a word, or short phrase, as you would find in a typical dictionary, should be contributed to the Wiktionary sister project instead.
Original source text, such as from a public-domain book that you want to post to make it more accessible, should be contributed to one of Wikipedia's other sister projects, Wikisource. For a list of all related projects, see the Complete list of Wikimedia projects.
We also tend to discourage authors from writing about themselves or their own accomplishments, as this is a conflict of interest. If you have notable accomplishments, someone else will write an article about you (eventually). Wikipedia:Autobiography has more detail on this.
As a general rule, do not copy and paste text from other sources. Doing so usually constitutes both a copyright violation and plagiarism. This general rule includes copying and pasting material from websites of charity or non-profit organizations, educational, scholarly and news publications, and all sources without a copyright notice. If a work does not have a copyright notice, assume it to be under copyright-protection. Brief quotations of copyrighted text may be used to illustrate a point, establish context, or attribute a point of view or idea. Use of copyrighted text must be in compliance with Wikipedia:Non-free content criteria policy.
Wikipedia does not generally prefer any particular standard variety of English (U.S. spelling vs. British spelling, for example) over another. Try to apply the principles listed below when editing:
1. Do not edit a page simply to "correct" a spelling that is correct in another standard form of English, unless it violates the principles listed here.
2. If the subject of an article is strongly related to a particular English-speaking country, then use the variety of English used for that country. So use American spelling for articles related to the United States, British spelling for articles related to the United Kingdom, etc.
3. If the subject of an article is not strongly related to any particular country ("Astronomy", for example), the original contributor's usage should be followed, and usage should be consistent throughout the article.