Thanks Robert for your reply

Till date we have used hyphens in sub domain & we have not seen any -ve impact.

We were creating a list of 1000 new colleges so i just wanted to be rest assured, that's y i raised Q.

Also Students are  aware of famous universities & colleges so thr is lot of search related to University specific keywords.

In some cases we have seen General level keywords like "Animation colleges Delhi" have less search compare to Particular university which is famous in Animation. In education we have seen thr is lot of search related to university & college level ky.

In hotel Industry its a vice versa

My website is related to education. We have created sub domains for all major colleges, universities & Entrance exams like Gre, Toefl ETC.

for eg:  amityuniversity.abc.com (Amity is Name of University )

Now if have to mention city name in URL as well (college is located in multiple locations)

amityuniversity-delhi.abc.com
amityuniversitydelhi.abc.com

Now my Q is can we use hyphens in sub domains if we have to add city name or shall we create without using any  hyphens.

In Directory  structure we can always separate words with hyphens, can we follow same practice in subdomain as well

Which is a  best URL for subdomain

amity-university-delhi.abc.com
amityuniversity-delhi.abc.com
or amityuniversitydelhi.abc.com