SN35.82 — Discourse on the World
Then a certain disciple approached the Blessed One... and, having sat to one side, that disciple addressed the Blessed One thus:
The world, the world, it is said, Venerable Sir. In what way, Venerable Sir, is it called the world?
It is, indeed, because it decays, disciple, that it is called the world. And what decays? The eye, disciple, decays. Forms decay, eye-consciousness decays, eye-contact decays, and whatever feeling arises with eye-contact as condition, whether pleasant, painful, or neither-painful-nor-pleasant, that too decays...
The tongue decays...
The mind decays, mental phenomena decay, mind-consciousness decays, mind-contact decays, and whatever feeling arises with mind-contact as condition, whether pleasant, painful, or neither-painful-nor-pleasant, that too decays.
It is, indeed, because it decays, disciple, that it is called the world.