Economic sustainability is the ability of an economy to support a defined level of economic production indefinitely. Since the Great Recession of 2008, this is the world’s biggest apparent problem, which endangers progress on the environmental sustainability problem.
Sustainability is what people want to happen indefinitely. No country has a GDP growth target less than about 2%, except when recovering from a recession. Thus the de facto definition of economic sustainability is steady growth in total national GDP of a minimum of about 2% per year.
But total national GDP doesn’t tell you how much the average person’s income is. Nor does it tell how many people are at the low end of the distribution of income and are thus starving.