He died of 'natural causes'. [=he died because he was ill or old and not by being killed in an accident, battle, etc.]
She was adopted immediately after she was born and never knew her 'natural' [=(more commonly) 'birth'] parents.
a country rich in 'natural resources' [=a country that has many valuable plants, animals, minerals, etc.]
(..) It's time to put this behind us. It's gone on too long. This has to stop. Dad... Things will take their natural course, Lindsey. Len, I appreciate everything you've done. You've been a great friend to me. That goes for Abigail, too. You've been a great friend to both of us. I want him dead. (..)2009 The Lovely Bones