 The relation is directional because even if ""t" entails "h"", the reverse ""h" entails "t"" is much less certain.Determining whether this relationship holds is an informal task, one which sometimes overlaps with the formal tasks of formal semantics (satisfying a strict condition will usually imply satisfaction of a less strict conditioned); additionally, textual entailment partially subsumes word entailment.Textual entailment can be illustrated with examples of three different relations