nContradiction: inconsistent, opposites
nJohn is a bachelor. John is married.
nI am happy. I am not happy.
nToday is Monday. Today is Tuesday.
nEntailment: S1 necessarily implies S2 is true
nThe park wardens killed the bear. è The bear is
dead.
nRobin is a man. è Robin
is a human.
nJill and Bill have just gotten married to each other. è Jill
and Bill are spouses.
nDavid is a Republican. è David is a human.