The question comes down to long-term sustainability: we need a certain area of land to sustain indefinitely a population of organisms, to grow food, collect water and absorb waste.

While frequent praise during the learning process can be beneficial, it can be hard to sustain indefinitely.

Moreover, debt would be on an upward path relative to the size of the economy, a trend that could not be sustained indefinitely.

On the piano, tremolo can create a seemingly louder and larger sound that can be sustained indefinitely.

They produce logs and are trying to manage their forest resources so that production can be sustained indefinitely.