Wikipedia:Title punctuation

The punctuation of titles is determined by common usage or the official name, just as with any other title. Titles are not followed with a period, even though sentence case is used. In general, titles are chosen to allow making the title bold in the lead sentence.

Specific topics and examples

 * Note: many of these proposed topics and examples are contrary to current guidelines in the WP:MOS.

Page names that only differ by punctuation
It is not acceptable to create two articles (on different topics) with titles that differ only in punctuation. If this arises, a separate form of disambiguation is needed, with a hatnote at the top of each page, linking each to a dedicated disambiguation page or to the other article. In the case of hyphens and diacritics add redirects from any likely alternative spellings.

Airports
Airport names are not commonly spelled with a dash, and only use a hyphen. A redirect can be created from a minus sign and a dash, but is not likely to be used and is not needed.

Comets
Comet names only use slashes, spaces, and hyphens. The name used is that established by the IAU, with the common name being preferred, with a redirect from the formal name. For example, in an e-mail from the IAU:"It is strictly not correct to write "Comet Hale-Bopp", but rather "Comet C/1995 O1 (Hale-Bopp)". Many comets carry the same name, so designations are paramount, not names; names are secondary. It's better to just put "Comet C/1995 O1" than "Comet Hale-Bopp"."

Hale-Bopp is the name, Comet C/1995 O1 the designation, so the article would be titled Comet Hale-Bopp, with redirects from Comet C/1995 O1 and Hale-Bopp. Technically the word comet is not a part of the name, just as planet is not a part of the name of a planet, and is not capitalized, although this is not universally practiced, as can be seen from the e-mail. Some dictionaries list comet Hale-Bopp with a lower case c, some list Halley's comet with a lower case c.

Repeating events
By using 2012 Summer Olympics or Summer Olympics of 2012, the lead sentence can incorporate that and facilitate making the title bold. Using Canadian federal election of 2008 or 2008 Canadian federal election over Canadian federal election, 2008 is preferred for that reason.

Expressions borrowed from other languages
Diacritics are used in many languages, and the title follows common usage, with redirects from other spellings – with or without diacritics.

Examples

 * Hyphens: Comet Hale-Bopp, Mexican-American War, Michelson-Morley experiment, Seattle-Tacoma International Airport, Wilkes-Barre, Olivia Newton-John
 * En dashes: History of the Soviet Union (1985–1991), with a redirect from History of the Soviet Union (1985-1991)
 * Diacritics: Papier-mâché, with a redirect from Paper mache, but Napoleon Abueva, with a redirect from Napoleón Abueva (Napoleon Abueva is more common, as is papier-mâché)