We only had enough room to pack the 'bare essentials'. [=the things that are absolutely necessary]
Reservations are 'essential' [='necessary, needed'] if you plan to eat there on a Saturday.
All action movies have 'essentially' [='basically, fundamentally'] the same plot.
(..) So, when the time comes... ... the boy must die? Yes. He must die. And Voldemort himself must do it. That is essential. - Where've you been? - I thought you went to the forest. I'm going there now. Are you mad? No... (..)2011 Harry Potter and the Deathly Hallows: Part 2