Interested in Language
For a year, her second home was the hospital(,) where she was being treated for cancer.
Is the comma optional? Thanks.
The only realistic justification for a comma that I can think of is if both parties in the conversation know that that a particular hospital is being referred to. This might be the case where, for example, one hospital serves a large area/population. This is possible but, in my opinion, far less likely than the comma-free defining clause. Like Mike, I think the comma is an error.