In the first sentence, the noun Vivek is the Subject. It answers the question, "Who threw a stone?" The group of words threw a stone is the Predicate. The Predicate contains the verb threw. What did Vivek throw? - A stone. Stone is the object which Vivek threw. Hence, the noun stone is called the Object. In the second sentence, the noun donkey is the Subject. It answers the question, "Who kicked the boy?" The noun boy is the Object. It answers the question, "Whom did the donkey kick?"