Reversive

Two predicates P and Q are said to be reversives iff they describe change in opposite directions, relative to some reference point R; if both P and Q take place (to the same extent), the change brought about by one predicate is undone by the other.

• Illustration
  • P = enter; P denotes a change of state from S₁ (x is outside) to S₂ (x is inside)
  • Q = leave; Q denotes a change of state from S₂ (x is inside) to S₁ (x is outside)

1. John entered the house (S₁ → S₂)
2. John left the house (S₂ → S₁)