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.]
(..) They may yet be alive. Less than a day ahead of us. Come. Come, Gimli! We're gaining on them! I'm wasted on cross-country. We Dwarves are natural sprinters. Very dangerous over short distances. Rohan. Home of the Horse-lords. There's something strange at work here. Some evil gives speed (..)2002 The Lord of the Rings: The Two Towers