user9943: I am wondering if the tags should be cleaned up. I made a few several unsuccessful attempts, because I don't know how to delete or merge tags.
For example experiment is a tag with 5 hits or so, but no definition. It should be removed, or at least synonymed with experimental-design, if you ask me. 
There are other examples, but I would like to know if it is possible to suggest such deletions. With less than 5 hits it is not possible to suggest synonyms, but that means that these needless tags keep in existence. Can anyone advise on ways to clean the tag list and get rid of largely unused tags?

user12909: If you don't mind borrowing ideas from other SE, here is what we do on math SE. This is done yearly too.

Tags need a regular cleanup. This is a customary thread for tag synonyms etc.
Rules of the game are basically the same:

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);
let's wait a couple of days before implementing a suggestion;
after the problem described in an answer is resolved, please edit it to say so.

(Of course if a proposal requires an extended discussion you can post it as a separate question.)


9943: <p>I am wondering if the tags should be cleaned up. I made a few several unsuccessful attempts, because I don't know how to delete or merge tags.</p>

<p>For example <strong>experiment</strong> is a tag with 5 hits or so, but no definition. It should be removed, or at least synonymed with experimental-design, if you ask me. </p>

<p>There are other examples, but I would like to know if it is possible to suggest such deletions. With less than 5 hits it is not possible to suggest synonyms, but that means that these needless tags keep in existence. Can anyone advise on ways to clean the tag list and get rid of largely unused tags?</p>
 12909: <p>If you don't mind borrowing ideas from other SE, <a href="https://math.meta.stackexchange.com/questions/19037/tag-management-2015">here</a> is what we do on math SE. This is done yearly too.</p>

<blockquote>
  <p>Tags need a regular cleanup. This is a customary thread for tag synonyms etc.</p>
  
  <p>Rules of the game are basically <a href="https://math.meta.stackexchange.com/q/12485/">the same</a>:</p>
  
  <ul>
  <li>post your suggestion as an answer here if you see
  
  <ul>
  <li>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),</li>
  <li>a tag that should be a synonym of an existing one,</li>
  <li>a tag that used for two or more completely unrelated things,</li>
  <li>a need to create a new tag;</li>
  </ul></li>
  <li>upvote/downvote/comment as your agree/disagree with suggestions (so please post different suggestions in separate answers);</li>
  <li>let's wait a couple of days before implementing a suggestion;</li>
  <li>after the problem described in an answer is resolved, please edit it to say so.</li>
  </ul>
  
  <p>(Of course if a proposal requires an extended discussion you can post it as a separate question.)</p>
</blockquote>
