How to remove record from join table

I'm able to add a record to a join table like this:

   e = Event.find(m)
   g = Group.find(n)
   e.groups << g

But how can I remove the record? I imagine something like

   e = Event.find(m)
   g = Group.find(n)
   e.g.destroy!

But I haven't found the right syntax yet. Anyone familiar with this?
Thanks!

I believe if you have both Event and Group as has_and_belongs_to_many
to each other, doing either e.destroy or g.destroy will automatically
remove the entry in the join table.