While reading about original sin, I often read that the Catholic and Orthodox churches disagree on the doctrine of original sin. But as far as I can tell, they both reject the idea that mankind inherited sin from Adam and believe that mankind only inherited the fallen nature. The only differences I see are in terminology. What am I missing? How are their views on original sin different?
Catholics (i.e., Western or Latin -- I belong to this group) believe that original sin entails actually inheriting the burden of Adam's Sin, which is mortal sin keeping us from entering heaven without a method of acquiring sanctifying grace, such as baptism. Original sin also threw all of nature into discord, and is the source of man's concupiscence. The Easter Orthodox, Eastern Catholics, and Oriental Orthodox, by contrast, do not believe that man inherits the burden of Adam's sin, but they believe that it is the source of the fallen nature of man, and concupiscence.
More info here: http://en.wikipedia.org/wiki/Original_sin
In Latin theology original sin does entails inheriting the burden of Adam's sin (in Latin reatum) referring to penalty (in CCC, stain of original sin) not guilt (lat. culpa). Therefore there is no substantial difference. People tend to conflate Protestant's original guilt into St. Augustine's original sin. With this being clarified there is no substantial difference between Greek view of First Motion (cf. St. Maximos the Confessor) and Latin view of Original Sin. This is why babies are born with mortality and concupiscence, we all need to be baptized for the remission of reatum not culpa.