When you look at questions currently tagged [tag:chebyshev-function], you will see questions from various areas there. (Number theory, Chebyshev polynomials, Chebyshev inequality,...) The [tag-info for this tag](http://math.stackexchange.com/tags/chebyshev-function/info) is currently empty.

My first guess would be that this tag is supposed to be used for questions about [Chebyshev functions](http://en.wikipedia.org/wiki/Chebyshev_function) such as $\vartheta(x)$ and $\psi(x)$, which are used in analytic number theory. (But there might be also some other meanings of this term I am unaware of.) 

I think that it would be good to:

 * Agree what this tag should be used for.
 * Fill in the tag-excerpt and tag-wiki, explaining when the tag should be used.
 * Clean up this tag. (Remove the tag from the questions belong there. Add the tag to the questions about Chebyshev functions.)
 * If incorrectly tagged questions will keep appearing even after the tag-wiki is added, we might also create a [comment template](http://meta.math.stackexchange.com/questions/4925/list-of-comment-templates/8587#8587) explaining correct usage of this tag.

 
But I wanted to get some input from other community members first.

<hr> 

I searched a bit whether this tag has already been discussed here on meta. The only thing I found was a mention of this tag in [this answer](http://meta.math.stackexchange.com/questions/16695/about-the-creation-of-a-bessel-functions-tag/16696#16696):

> Cautionary tale: [tag:chebyshev-function] is full of questions about Chebyshev-whatever, but not -function. At a glance, I have not found a single question about actual [Chebyshev functions](http://en.wikipedia.org/wiki/Chebyshev_function) there. It is not unusual for rarely-used tags with few followers to degenerate into such a mess. 

<hr>

**EDIT:** Since nobody objected to the idea that this tag - if we keep it - should only be for questions about Chebyshev functions in number theory, I went ahead and created [tag-wiki](http://math.stackexchange.com/posts/1146602/revisions) and [tag-exceprt](http://math.stackexchange.com/posts/1146603/revisions).

I have also started retagging questions which do not belong here, see [this list](http://chat.stackexchange.com/transcript/message/20012289#20012289). They are mostly about Chebyshev polynomials and Chebyshev inequality. Since I am not very familiar with these two topics, some people with more experience in these areas might have a look at those questions and choose better tags, if needed. 

Of course, if there is support for the suggestion to get rid of the tag entirely - as suggested in the other answer - this still can be done. (Although in that case we will have remove the tag-wiki, since the tags having tag-wiki [are not removed from the system](http://meta.stackexchange.com/questions/127700/do-not-expire-single-use-tags-that-have-a-tag-wiki).