grosbouff

Pencil Wiki is a simple wiki solution for your WordPress.
Basically, it adds new roles & capabilities that allow your users to add/edit wiki pages (custom post type).
It comes with several widgets and custom templates (that you can override) fully integrated with the Twenty Twelve theme.
Pages are edited backend, but there is a menu on every wiki page with the necessary links; and a wiki index / search input.
Only Administrators and Editors can create new wikis (top-level pages); and Wiki Authors can add pages to it. 
Administrators and Editors can also LOCK some wiki pages (for any reason) or branches; which means they will not be editable anymore by other users.
I voluntarily made the plugin quite simple to avoid making it intrusive (javascript, css, …) and put too many features. I recommend to run it with those plugins : 
* <a href="https://wordpress.org/extend/plugins/member" rel="ugc">Members</a>Members by Justin Tadlock, to manage roles and capabilities 
* <a href="http://mtekk.us/code/breadcrumb-navxt" rel="nofollow ugc">Breadcrumb NavXT</a> by John Havlik, to generate breadcrumbs 
* <a href="https://wordpress.org/extend/plugins/simple-footnotes" rel="ugc">Simple Footnotes</a> by Andrew Nacin, to put footnotes in your wiki pages.
WordPress has a revision system, which is perfect for a wiki. 
Unfortunately, I didn’t find a way to customize it (add revision messages, etc).

Pencil Wiki

Pencil Wiki is a simple wiki solution for your Wordpress.

Wikimedia Foundation

Enhance your website with free knowledge straight from Wikipedia!
Install Wikipedia Preview, the free add-on designed to better engage your visitors and improve the user experience on your website.
The Wikipedia Preview plugin provides context to your site’s visitors with content directly from Wikipedia. It allows you to add links to your content so that when your visitors click or hover on them, they see a pop-up box with information and images straight from Wikipedia. With Wikipedia Preview your visitors gain context on a topic, without ever leaving your website.
Wikipedia Preview is an official plug-in designed and developed by the <a href="https://wikimediafoundation.org/" rel="nofollow ugc">Wikimedia Foundation</a>, the non-profit behind Wikipedia and other free knowledge projects.
The plug-in is entirely free to download and use, in line with the Wikimedia Foundation’s mission to provide free knowledge for everyone.
<iframe loading="lazy" title="Wikipedia Preview | Free website plug-in" width="750" height="422" src="https://www.youtube.com/embed/_m6YzR0j8Fs?feature=oembed" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>
Benefits
<ul>
<li>Rich-media content straight from Wikipedia, to give your site’s visitors the context they need, without ever having to leave your website.</li>
<li>Always free.</li>
<li>Available in 300 languages.</li>
<li>Easy to set up. Adding Wikipedia Preview links is even easier than adding other hyperlinks.</li>
<li>Leveraging the content and brand name of one of the most popular websites in the world.</li>
</ul>
Features
<ul>
<li>Can be set up using the same process you use to add hyperlinks to your articles or using the Gutenberg editor custom tool.</li>
<li>Handles any link to a Wikipedia article regardless of language, lead image presence or length.</li>
<li>Site owners can choose a specific section of an article as a preview, not limited to just the lead section.</li>
<li>Supports dark mode option for improved readability.</li>
<li>Works for Right-to-Left (RTL) and Left-To-Right (LTR) languages.</li>
<li>Offers access to a built-in gallery to dive into article images.</li>
<li>Can be disabled for any page using the post metadata sidebar.</li>
<li>Uses Gutenberg editor custom tool to search for Wikipedia articles and visualize Wikipedia Preview for readers.</li>
</ul>
How to add preview links to your site
Option 1 – How to add Wikipedia Preview links using the Classic Editor:
<ul>
<li>Add a Wikipedia article link to your site’s content using the same process you use to add hyperlinks to your articles.</li>
</ul>
Option 2 – How to add Wikipedia Preview links using the Gutenberg/ Block Editor:
<ol>
<li>Highlight the text you want to link to a Wikipedia article.</li>
<li>Select ‘W’ – Wikipedia Preview icon from the menu.</li>
<li>You will see a list of suggested articles. Select the one you want to link to.</li>
<li>Wikipedia Preview will automatically turn the link into a preview of the relevant Wikipedia article. You can easily customize the preview content by selecting a specific section of the article.</li>
</ol>

Wikipedia Preview

Textbook implementation. Also, this is just a fun way to add more interactivity to your blog, plus possibly learn something new.

Textbook

Fantastic plugin

Wikipedia Preview lets you show a popup card with a short summary from Wikipedia when a reader clicks or hovers over a link.

Pencil Wiki vs Wikipedia Preview