The state or condition of being unsustainable.(noun)
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Use "unsustainability" in a sentence
"I am not saying the native Americans were perfect, but unsustainability is not one of their culture's faults."
"I suspect that chavismo knows the long term unsustainability of these programs and that might be the reason in part behind some of the recent moves of the government."
"His arguments about the long term unsustainability of trade imbalances between nations make more sense than the nonsense peddled above at least."