can i watch To aru kagaku no railgun S if i havent watched to aru majutsu no index ?

To Aru Kagaku no Railgun S is telling the same event as To Aru Majutsu no Index. However, the main character and the perspective view of To Aru Kagaku no Railgun is Misaka Mikoto, while To Aru Majutsu no Index is Touma Kamijou.

There are some events in which only Misaka knows and some events in which only Touma knows. Therefore, there are some parts which can only be seen in the other anime.

I think it is fine to watch To Aru Kagaku no Railgun S even if آپ haven't watched To Aru Majutsu no Index since the story about the sisters is مزید related to Misaka. However, آپ might miss some small details.