Wikipedia:Simplified Manual of Style

Article titles and section titles should be in sentence case. "Rules and regulations", not "Rules and Regulations".

The English Wikipedia prefers no major national variety of the language over any other. These varieties (e.g. U.S. English, British English) differ in vocabulary (soccer vs. football), spelling (center vs. centre), and occasionally grammar (see Plurals, below).

Capitalize names of scriptures like "Bible" and "Qu'ran", but not "biblical". Capitalize "God" when used to mean YHWH.

Don't capitalize summer, winter, spring, fall, and autumn.

Don't capitalize names of plants and animals. Special cases include scientific names ("Homo sapiens"), birds, and proper nouns.

Circa [I don't know what to write here; the word is often used but our guidelines conflict.]

Write "US" or "U.S.", but not "USA".

Don't use the & sign, except in titles like AT&T.

Italicize names of books, films, TV series, music albums, paintings, and ships, but not songs; songs should be in quote marks.

Use   or {{nowrap}} to prevent a line from ending in the middle of expressions like 17 kg, AD 565, 2:50 pm), £11 billion, June 2025, 5° 24′ 21.12″ N, Boeing 747, after the number in 123 Fake Street and before Roman numerals in World War II and Pope Benedict XVI. Use   in the same way inside a wikilink.

Use straight quote marks and apostrophes that you probably find next to your keyboard's Enter key, that is, " and ', not the slightly different-looking “, ”, ‘, ’, etc.

Use logical punctuation. For example, "Hello, world", she said. Do not write it as "Hello, world," she said. (notice how the punctuation changed)

An ellipsis should be written as three separate dots ... not the one character … and not the spaced-apart . . .

Serial commas, like the second comma in "ham, chips, and eggs", are optional, so don't edit-war over them.

Avoid comma splices.

A hyphen is not used after a standard -ly adverb (a newly available home).

A hyphen shouldn't be between two spaces (when visible). Instead, use and en dash – with an   before and a space after, or use an em dash — without the spaces. See Wikipedia:How to make dashes. Don't use two hyphens -- to make a dash. And don't use a hyphen for a minus sign.

Use an en dash, not a hyphen, between numbers like "pp. 14–21".

Write "No. 1" or "number 1", but not "#1". Comic books are an exception.

It doesn't matter how many spaces come after a period, because extra spaces won't show.

Either 10 June 1921 or June 10, 1921, is OK. Either 400 AD or 400 CE is OK. Either 400 BC or 400 BCE is OK. Please, no edit wars.

Write one, two, three, ... eight, nine, not 1, 2, 3, 4, 5, 6, 7, 8, 9 (although there are many exceptions).

Write 12,000 for twelve thousand, not 12.000.

Either "James' house" or "James's house" is OK.

Usually avoid words like "I", "we", and "you", except in quotations and titles. Similarly avoid phrases like "note that", "remember that", "of course", "obviously" etc.

Picture captions should start with a capital letter. They shouldn't end in a period unless they are complete sentences.

Use wikilinks for the phrases most likely or most helpful to be clicked, and only those. Make sure each link goes to an article on the intended subject, and not to a disambiguation page.