A wiki is an online collaboratively edited hypertext publication, the most famous of which is Wikipedia. Wikitext is the markup language used by wikis. Its syntax is similar to a mix of Markdown and HTML.
## Syntax
`<!--- comments are hidden when reading, but visible when editing --->`
Section headings are bracketed by `=`. They go from `= One equal sign =` to `====== Six equal signs ======`. They are equivalent to Markdown's hashtag headings, from `# One hashtag` to `###### Six hashtags`. Why six in both? I believe it's because HTML has six levels of headings, from `<h1>` to `<h6>`.
Note that the `= One equal sign =` heading actually corresponds to the title of the page, and so cannot actually be used within a page. Consequently, the least number of equal signs is `== Two equal signs ==`.
Subscripts and superscripts can be written as `x<sub>1</sub>` and `x<sup>1</sup>`. Alternatively they can be written by the `<math>` tag (see below). `<small>Small</small>` and `<big>big</big>` texts are rarely used.
:Each colon creates an indentation three characters wide.
::and they can be nested.
```
`*` Unnumbered lists start with `*`, and numbered lists start with `#`. <br>
 `**` Lists can be nested <br>
  `***` for arbitrarily many levels.
The syntax for tables is [very complicated](https://en.wikipedia.org/wiki/Help:Table). The simplest of the [simple tables](https://en.wikipedia.org/wiki/Help:Basic_table_markup) is as follows:
Be warned that the newlines in a wikitext table are meaningful. Deleting a single newline above would completely change the shape of the rendered table.
You can insert images, audios, videos, or other forms of media by `[[File:Image.png|thumb|right|Image caption]]`. All media files must be hosted on [Wikimedia Commons](https://commons.wikimedia.org/wiki/Main_Page).
{{Quote|text=Quotation text.|title=Title|author=Author|source=Location in the publication}}
```
A "[non-breaking space](https://en.wikipedia.org/wiki/Non-breaking_space)" is a whitespace that should not be separated by linebreaks, such as the whitespace in "400 km/h". This is written as `400&nbsp;km/h`.
Extra whitespaces can be specified by `pad` tag. For example, `{{pad|4.0em}}` is a white space with length 4.0 [em-dashes](https://en.wikipedia.org/wiki/Dash#Em_dash).
If a word is interrupted by a link, it is "blended" into the link. For example, `[[copy edit]]ors` renders to [copy editors](https://en.wikipedia.org/wiki/copy_edit).
Templates are macros for wikitext, and they look like `{{template name|attribute=value|...}}`. There are thousands of templates, but only a few are in common use.
The most (in)famous one is the \[citation needed\]`{{cn}}` template. Note that `{{cn}}` is synonymous with `{{citation needed}}`, as one template can have many names.
`{{reflist}}` is usually put at the ends of pages, to generate a list of references used in the page.
An `infobox` template is, as it says, a template for a box containing information. Usually, each page contains at most two infoboxes, one on top and one on bottom. For particularly detailed pages, there can be more than two.
The infobox on the top is usually used to compactly display tabular information. They are common for biographies, geographical locations, and such. For example, the top infobox for [Euler](https://en.wikipedia.org/wiki/Leonhard_Euler) is:
| death_date = {{nowrap|{{death date and age|df=y|1783|9|18|1707|4|15}}}} {{awrap|{{bracket|[[Adoption of the Gregorian calendar#Adoption in Eastern Europe|OS]]: 7 September 1783}}}}
...
}}
```
The infobox at the bottom is usually used to display a curated table of related links. For example, the bottom infobox for [Euler–Lagrange equation](https://en.wikipedia.org/wiki/Euler%E2%80%93Lagrange_equation) is just `{{Leonhard Euler}}`, which displays a box containing links to many of the things named after Euler.
`~~~~` is used to sign on talk pages, and expands to something like `Username (talk) 10:50, 12 June 2023 (UTC)`.
`<math display=block></math>` renders to $$E = mc^2$$.
One can also include math using [HTML renders](https://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style/Mathematics#Using_HTML) or even by [plain Unicode](https://en.wikipedia.org/wiki/Mathematical_operators_and_symbols_in_Unicode). These are less flexible but more compatible with older browsers. Further, parts of Wikipedia syntax themselves are incompatible with `<math>`, such as in section titles or some templates, forcing the use of HTML or Unicode in such cases.
One should generally use a templated citation, like `<ref>{{cite web|url=https://example.com/|title=Example|date=2001|access-date=2023}}</ref>`. There are three forms of citation templates: [`cite web`](https://en.wikipedia.org/wiki/Template:Cite_web), [`cite journal`](https://en.wikipedia.org/wiki/Template:Cite_journal), [`cite book`](https://en.wikipedia.org/wiki/Template:Cite_book).
A citation can be named as `<ref name="X">...</ref>`. It can then be invoked as `<ref name="X" />`. The instance `<ref name="X">...</ref>` can go before or after `<ref name="X" />`. Any ordering would render to the same page.
## Typical Wikipedia page
```wikitext
{{Short description|One sentence summary of page}}
{{Infox box at the top
|infobox_data_1=...
|...
}}
[[File:Image of X.png|thumb|right|Image caption]]
The concept '''X''' is usually bolded. Now define the concept X. For non-specialist pages, this section should be written in plain language, with jargons defined in-line. Some [[link]]s would help.
== Introduction ==
Here one usually sets up the notation, overviews the history, and such. Details follow in the next sections.
Footnotes are numbered separately from inline references.{{NoteTag|note=Footnote text.}}
== Relation to Y ==
{{Main|Y}}
{{See also|Another page}}
Something about the relation between X and Y.
== See also ==
* [[Very relevant link]]
* [[Less relevant link]]
== External links ==
* [https://example.com/ External link one]: Summary of what is in the external link.
== Footnotes ==
<referencesgroup="note"/>{{Notelist}}
== References ==
<!-- generates list of references from inline reference tags, with columns with a minimum width of 30 em-dashes. -->
