Question: New year, new tag management thread.

Rules of the game are basically [the same](https://math.meta.stackexchange.com/q/27653/43351):

* Post your suggestion as an answer here if you see
	+ A particularly bad tag (a rule of thumb: «if I can't imagine a person classifying a tag as either interesting or ignored, I'm getting rid of it»),
	+ A tag that should be a synonym of an existing one,
	+ A tag that used for two or more completely unrelated things,
	+ A need to create a new tag;
* Upvote/downvote/comment as your agree/disagree with suggestions, so please post different suggestions in separate answers;
* Wait a couple of days before implementing a suggestion.
* After the problem described in an answer is resolved, please edit it to say so.
* If your tag suggestion exists in a separate question, please provide a link to the question in your suggestion.

See also:

* The [list with pending and approved synonyms](https://math.stackexchange.com/tags/synonyms).
* The [tagging chatroom](http://chat.stackexchange.com/rooms/3740/tagging) for extended discussion on tagging.
* [Last year's thread](https://math.meta.stackexchange.com/q/27653/43351) to look for suggestions that need to be implemented.

Also, note that one may use `[tag:calculus]` for [calculus](https://math.stackexchange.com/questions/tagged/calculus "show questions tagged 'calculus'"), i.e. tags on the main site, and `[meta-tag:discussion]` for [discussion](/questions/tagged/discussion "show questions tagged 'discussion'"), i.e. for tags on the meta site.

Answer: 
> 
> **Partially Resolved:** [singularvalues](https://math.stackexchange.com/questions/tagged/singularvalues "show questions tagged 'singularvalues'") is now [singular-values](https://math.stackexchange.com/questions/tagged/singular-values "show questions tagged 'singular-values'"), but the tag still lacks usage and a wiki.
> 
> 
> 

**Proposal: rename "singularvalues" to "singular-values"**

There's no usage guidance and tag wiki yet.
**Proposal: Rename [collatz](https://math.stackexchange.com/questions/tagged/collatz "show questions tagged 'collatz'") to [collatz-conjecture](https://math.stackexchange.com/questions/tagged/collatz-conjecture "show questions tagged 'collatz-conjecture'").**

Although Lothar Collatz is most known for the $3x+1$ problem (the Collatz Conjecture), I don’t think their names should be used interchangeably. Furthermore, the latter tag has a more informative name.