Wikipedia:Naming conventions (use English)

The title of an article should generally use the version of the name of the subject that is most common in the English language, as you would find it in reliable sources (for example other encyclopedias and reference works, scholarly journals, and major news sources). This makes it easy to find, and easy to compare information with other sources. Often this will be the local version, as with Madrid. Sometimes the usual English version will differ somewhat from the local form (Aragon, Venice, Normandy; Franz Josef Strauss, Victor Emmanuel III, Christopher Columbus). Rarely, as with Germany or Mount Everest, it will be completely different.

If an examination of the sources in an article shows that one name or version of the name stands out as clearly the most commonly used in the English language, we should follow the sources and use it. Whenever something else is demonstrably more common in reliable sources for English as a whole, and this is not a question of national varieties of English, use that instead.

Names not originally in a Latin alphabet, as with Greek, Chinese, or Russian, must be transliterated into characters generally intelligible to literate speakers of English. Established systematic transliterations (e.g., Hanyu Pinyin and IAST) are preferred. Nonetheless, if there is a common English form of the name, this is preferred over a systematically transliterated name; thus, use Tchaikovsky or Chiang Kai-shek, even though those are unsystematic. For a list of transliteration conventions by language, see Romanization and Category:Wikipedia Manual of Style (regional).

The native spelling of a name should generally be included in parentheses, in the first line of the article, with a transliteration if the Anglicization isn't identical. Redirects from native and other historically relevant names are encouraged. Where there is an English word or an exonym for the subject but a native version is more common in English-language usage, the English name should be mentioned but should not be used as the article title.

Include alternatives
The body of each article, preferably in its first paragraph, should list all frequently used names by which its subject is widely known. When the native name is written in a non-Latin script, this representation should be included along with a Latin alphabet transliteration. For example, the Beijing article should mention that the city is also known as Peking, and that both names derive from the Chinese name 北京. It is also useful to have multiple redirects to the main article, for example Sverige is a redirect to Sweden. If there is a significant number of alternative names or forms, it may be helpful to keep only the most common two or three in the first paragraph and a list of them in a separate section or footnote to avoid cluttering the lead; see Freyr for an example of this.

Modified letters
The use of modified letters (such as accents or other diacritics) in article titles is neither encouraged nor discouraged; when deciding between versions of a word that differ in the use or non-use of modified letters, follow the general usage in reliable sources that are written in the English language (including other encyclopedias and reference works). The policy on using common names and on foreign names does not prohibit the use of modified letters, if they are used in the common name as verified by reliable sources.

In general, the sources in the article, a Google book search of books published in the last quarter-century or thereabouts, and a selection of other encyclopaedias should all be examples of reliable sources; if all three of them use a term, then that is fairly conclusive. If one of those three diverges from agreement then more investigation will be needed. If there is no consensus in the sources, either form will normally be acceptable as a title.

Place redirects at alternative titles, such as those with or without diacritics. Add R to diacritics or R from diacritics below the redirect to properly categorize it, such as for print editions.

Search engines are problematic unless their verdict is overwhelming; modified letters have the additional difficulties that some search engines will not distinguish between the original and modified forms, and others fail to recognize the modified letter because of optical character recognition errors.

One recurrent issue has been the treatment of graphemes such as ae and oe. By and large, Wikipedia uses œ and æ to represent the Old Norse and Old English letters. For Latin- or Greek-derived words, use e or ae/oe, depending on modern usage and the national variety of English used in the article. German proper names should be treated with care and attention to practice. Notice that even in German, combinations such as oe are used in some names rather than umlauts (as in Emmy Noether and, in modern German, Johann Wolfgang von Goethe).

Beware of overdramatising these issues. As an example, Manual of Style/Ireland-related articles may be mentioned, which—as a side-effect— regulated use of diacritics regarding Ireland-related articles before, during, and after an extensive dispute on the question of diacritics in 2005, such as Inishmore and not Inis Mór, or Tomás Ó Fiaich and not Tomas O'Fiaich (see the aforementioned MoS page for details).

Established usage in English-language sources
If a particular name is widely used in English-language sources, then that name is generally the most appropriate, no matter what name is used by non-English sources.

Divided usage in English-language sources
Sometimes, English usage is divided. For example, US newspapers generally referred to the "Olympics in Torino", following official handouts; however, newspapers in other parts of the English speaking world referred to it taking place in Turin. In this case, we cannot determine which is "most common". Use what would be the least surprising to a user finding the article. Whichever is chosen, one should place a redirect at the other title and mention both forms in the lead.

Search-engine hits are generally considered unreliable for testing whether one term is more common than another, but can suggest that no single term is predominant in English. If there are fewer than 700 hits, the count (from the final page of hits)  be accurate for the engine's particular corpus of English, but whether this represents all English usage is less certain. If there are more than 700 estimated hits, the number from the last page be wrong; a search engine loads only a limited number of hits, no matter how many there are. Counts over 1,000 are usually estimates, and may be extremely inaccurate. If several competing versions of a name have roughly equal numbers (say 603 for one variant and 430 for another), there may well be divided usage. When in doubt, search results should also be evaluated with more weighting given to verifiable reliable sources than to less reliable sources (such as comments in forums, mailing lists and the like). Also, consult reliable works of general reference in English.

Wikipedia is not a crystal ball. It is not our business to predict what term will be in use, but rather to observe what is and has been in use and will therefore be familiar to our readers. If Torino ousts Turin, we should follow, but we should not leap to any conclusion until it does.

When there is evenly divided usage and other guidelines do not apply, leave the article name at the latest stable version. If it is unclear whether an article's name has been stable, defer to the name used by the first major contributor after the article ceased to be a stub.

No established usage in English-language sources
It can happen that an otherwise notable topic has not yet received much attention in the English-speaking world, so that there are too few sources in English to constitute an established usage. Very low Google counts can but need not be indicative of this. this happens, follow the conventions of the language in which this entity is most often talked about (German for German politicians, Turkish for Turkish rivers, Portuguese for Brazilian municipalities etc.).

If, as will happen, there are several competing foreign terms, a neutral one is often best. Wikipedia:Naming conventions (geographic names) § Multiple local names and § Use modern names express some ideas on resolving such problems.