skos for a changing term definition list

[henk l]

I would like to build a list of concepts with definitions. Skos seems to be well suited for this. I will use skos:concept for the terms and skos: definition for the definitions.

But:

• there are concepts that have changed their definitions in time, I need to model that, but how is this done the best way?
  
• there are concepts that simultanously have different definitions, because of diffferent institutional context or different selection criteria; like definitons of "unemployment" can differ because the population to which it can apply can be defined differently, by age, time not working etc. Still the basic concept stays the same. Can this be done with several skos:defiintions related to one concept?

So, the primary question is: is skos sufficient here, or should I look for other vocabularies too?