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.]
(..) years worth of tampons? Well. - When did your mother go into menopause? - Okay. I'm not talking about this with you. Oh,penny,this is a natural human process,and we're talking about statistically significant savings. Now,if you assume tampons per cycle and a -day cycle... are you fairly regular? (..)2007 TvShow: The Big Bang Theory Title: The Luminous Fish Effect Season: 1 Episode 4