One single session in hair transplant: Hair Transplant proceedure performed either by one or more hair transplant techniques on a single given patient on the same (single) day.
If a session is performed on a given patient first day and another session is performed on second day, its NOT called as single session. They are called multiple sessions.
If a session is performed on a given patient and another session is performed on a different patient on the same day, its NOT termed as single session.