Reversible vs Non reversible work

[Miles John-Baptiste 3C]

What makes work reversible or non-reversible?

[Nina Chessa 2A]

If work is done infinitesimally, that is, in really small steps, then it is considered a reversible process. This is because it can be reversed by an infinitesimal (infinitely small) change. Non-reversible work occurs when a measurable change (not very small) happens and cannot be reversed by an infinitesimal change. For example, if the external pressure on a piston differs from the pressure inside the piston by a measurable amount, changing the pressure on the external by an infinitesimal amount does not cause the piston to move in the opposite direction (it cannot be reversed).