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.]
(..) the future can be extremely dangerous. Even if your intentions are good, it can backfire drastically. Whatever you've got to tell me I'll find out through the natural course of time. Dear Dr. Brown: On the night that I go back in time... ... you will be... ... shot by terrorists. (..)1985 Back to the Future
(..) - Yeah. Yeah. - All right. There she is. Just go in there and invite her. GEORGE: But I don't know what to say. MARTY: Say anything. Say whatever's natural, the first thing that comes into your mind. Nothing's coming to my mind. Jesus. It's a wonder I was even born. - What? What? - Nothing. (..)1985 Back to the Future