( ( A ( positive sign ) ) ( ( represents ( an ( endothermic reaction ) ) ) . ) )
(ROOT (S (NP (DT A) (JJ positive) (NN sign)) (VP (VBZ represents) (NP (DT an) (JJ endothermic) (NN reaction))) (. .)))
A positive sign represents an endothermic reaction.
(ROOT (S (S (VP (VBZ Is) (NP (NP (DT the) (NN heat)) (PP (IN of) (NP (NP (NN reaction)) (PP (IN for) (NP (DT an) (JJ endothermic) (NN reaction)))))))) (VP (VBZ is) (ADJP (JJ positive))) (. .)))