I want to know the answer to the following question:
What is it called when the last Imam or his unborn successor goes into concealment?
All the background I'm provided with is that "When the dynastic line of the separating successor Imam ended with no heir to succeed him, then either he (the last Imam) or his unborn successor was believed to have gone into concealment, that is, The Occultation.". Is that enough to answer the question?
Answer: yes