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.]
(..) but I just can't bear going around in black. It's bad enough not being able to go to any parties... ...but looking this way too. I don't think you're at all horrible. It's only natural to want to look young and be young when you are young. Oh, baby.... How would you like to go visiting somewhere? (..)1939 Gone with the Wind