Hi, 
I have been recently admitted in one of the German universities. Everything went well, and I applied also for my visa at New Delhi. I have also successfully received a notification to submit my passport at one of the VFS offices. But, unfortunately I am not able to travel this semester due to some family issues. 
My question is what should I tell the visa authorities? Is it possible to also defer a visa for next semester/year. Or will I have to apply for it again after cancelling this visa?

No, you need to apply again. As simple as that. Student visa's or extensions will always tie with the exact date of studies. However, you can do following:
-Get the visa stamped now. If you are lucky you may end up getting 1-year visa in the beginning itself
-Explain your family situation to Uni and get the assurance for next semester
-Come here and get the extension done

Hi,
thanks for a quick reply. What are the chances of getting 1-year visa in the beginning itself? As per my information, in my country (India) students get only a 3-month visa in the beginning, which has to be extended in the host country afterwards. 
Also, if I get already the visa and do not go afterwards to Germany, don't I have to inform the embassy regarding my decision. Because  afterwards again I have to apply for the visa next semester.