> ### Notes

> * This thread is open and unlocked only because [the community decided to make an exception][exception]. Please **do not** use this question as evidence that you can ask similar questions here. Please **do not** create additional [tag:showcase] questions.

> * This is no longer a [tag:popularity-contest], nor are snippet lengths limited by the vote tally. If you know this thread from before, please make sure you familiarize yourself with the changes.

This thread is dedicated to showing off interesting, useful, obscure, and/or unique features your favorite programming languages have to offer. This is neither a challenge nor a competition, but a collaboration effort to showcase as many programming languages as possible as well as possible.

### How this works

* All answers should include the name of the programming language at the top of the post, prefixed by a `#`.

* Answers may contain one (and only one) factoid, i.e., a couple of sentences without code that describe the language.

* Aside from the factoid, answers should consist of snippets of code, which can (but don't have to be) programs or functions.

* The snippets do not need to be related. In fact, snippets that are *too* related may be redundant.

* Since this is not a contest, all programming languages are welcome, whenever they were created.

* Answers that contain more than a handful of code snippets should use a [Stack Snippet] to collapse everything except the factoid and one of the snippets.

* Whenever possible, there should be only one answer per programming language. This is a community wiki, so feel free to add snippets to any answer, even if you haven't created it yourself. There is a [Stack Snippet for compressing posts][compress], which should mitigate the effect of the 30,000 character limit.

Answers that predate these guidelines should be edited. Please help updating them as needed.

### Current answers, sorted alphabetically by language name



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[compress]: http://codegolf.meta.stackexchange.com/q/10734/12012
[exception]: http://codegolf.meta.stackexchange.com/q/10656/12012
[Stack Snippet]: https://stackoverflow.blog/2014/09/introducing-runnable-javascript-css-and-html-code-snippets/