How to deal with elasticity/flexibility in HSK vocabulary? I'll be concise for those knowledgeable, and refer to brief and basic bibliography for those who are not.

The Chinese elasticity/flexibility is a lexical property of Chinese terms, two sides of the same coin, which must be reflected in the very same entry for a certain lemma.

Therefore, for example the fifth version of the prestigious XDHYCD (Xiandai Hanyu Cidian) applies mutual annotations in the respective entries (however, this criterion is not enough for a comprehensive treatment), so that the entry for 煤 mei ‘coal’ reads "noun, … also called 煤炭 mei-tan ‘coal-charcoal’", and the entry for 煤炭 meitan ‘coal-charcoal’ is annotated as "noun, 煤 mei ‘coal’".

Furthermore, it would improve greatly studying resources to add the relationship between such "elasticity" and the surviving morphemes in truncated abbreviations and similar phenomena, such as what Prof. Ceccagno coined "metacompounds". For example, the apparent surviving morphemes that appear in 卫视 'satellite T.V.' are at least the bound short version of the disyllabic elastic words 卫星 'satellite' and 电视 'television'.

Please, before commenting, read the following brief article (and if necessary further references within it); if you still have any questions, I'll be glad to try and answer them.

Finally, elasticity from Xiandai Hanyu Cidian 2005 has been tabulated in the following open access thesis.

I hope an enriching discussion ensues for this critical lexicographical and pedagogic issue.
One of the difficulties for learners is becoming familiar with when to use the short and when to use the long form. In most cases, at least for beginner/intermediate levels, my impression is the rule “use the long form, not the short form” is generally a good heuristic. I think most students learn this by experience.

Let’s take a basic, concrete example: 学/学习. 

Using the ABC English-Chinese Dictionary as reference we have the following for 学:


  Verb: 
  
  1: study; learn; 
  
  学文化 xue2wen2hua4 learn to read and write
  
  2: imitate;mimic
  
  Bound form: 
  
  1: learning; knowledge in 学问
  
  2: subject of study; branch of learning in 学科
  
  3: school; college in 学校,大学


It probably would indeed be better if the above entry were completed by adding “Long form: 学习” to the “Verb: 1 Study…” section. But generally students are taught the long form, 学习, first and so learn the short form at the same time. So I don’t think it’s a critical issue for people learning the language, but perhaps it would be helpful for some students to have some explanation.

The only other usage I can think  of (I’m about B1/B2 level) for the short form is 

学到老，学不了 / 活到老，学到老。

It’s not a vital thing to be able to say… But still, it’s good to be able to understand it.

So, my take on this is that it’s an interesting notion for linguists, but not a vital concept that has to be explained to all students of the language.