premise: A skateboarding youth does a trick on a rail. hypothesis: A young person on a skateboard.
entailment: Skateboarding youth implies a young person.  A skateboarding youth must be on a skateboard in order to do a trick on a rail.|entailment: Youth describes a young person. A young person is skateboarding, so they must be on a skateboard.|entailment: you have to get on the skate board before doing tricks.