I am writing a research paper with three scenarios. The first is called "the inflexible", the second is "the flexible", and the third is between them. I have difficulty to find a term for it. I thought about words "standard", "normal", and "ordinary", but they also imply that the other two cases are not standard or normal, which is not the case. The words "median", "intermediate" or "mean" also do not sound very well. Can anyone help me with this?
In the flexible case, changing the capacity of production requires building a new facility, thus incurring a very high cost. In the inflexible case, just a reconfiguration of the current production line is required. The third case is somewhere in between.
Based on the above-mentioned context you provided in comments, here's an idea.
If your analysis is based on investment or cost, then it stands to reason to use the appropriate nouns. I believe that would help make your message more clear.
High-investment scenario. This involves building a new production facility, thus incurring a very high cost.
Low-investment scenario. In this scenario, only a reconfiguration of the current production line is required.
Medium-investment scenario requires purchasing new equipment and certifying new personnel.
You can likewise use high-cost, medium-cost, and low- or zero-cost scenarios.
It seems these alternatives fit the context well, if I understood your situation correctly.
As suggested above, either go with semiflexible or choose a neutral word for the middle category (eg. standard, default, non-specialized, etc).
The other option is to use words that denote varying degrees of flexibility: static (not flexible), plastic (can tolerate some flexibility), and elastic (flexible enough to shape and reshape).