What is economic growth here? Piketty discussed the return on capital versus earnings. He doesn't claim one is superior to the other, or even that in the long

What is economic growth here? Piketty discussed the return on capital versus earnings. He doesn't claim one is superior to the other, or even that in the long run one will certainly trump the other. He simply argues based on the evidence that it is likely that in the long run, because it appears that the long trend is negligible economic and demographic growth, there is no intrinsic law within capitalism that ensures capital returns will not become so important that inequality can reach massive levels.