Two way doors, reversible, bidirectional, symmetrical

One way doors, irreversible, unidirectional, entropy, broken symmetry / asymmetrical

Shown: One way door (water elevator). You go up but you can’t go back the way you came.

Two way doors, reversible, bidirectional, symmetrical

One way doors, irreversible, unidirectional, entropy, broken symmetry / asymmetrical

Shown: One way door (water elevator). You go up but you can’t go back the way you came.