( ( ( ( Activation energy ) , ) ( which ( is ( defined ( as ( ( the amount ) ( of ( energy ( required ( to ( make ( the reaction ) ) ) ) ) ) ) ) ) ) ) ) ( ( ( ( start and ) carry ) ( on spontaneously ) ) . ) )
(ROOT (S (NP (NP (NN Activation) (NN energy)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (VP (VBN defined) (PP (IN as) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN energy)) (VP (VBN required) (S (VP (TO to) (VP (VB make) (NP (DT the) (NN reaction))))))))))))))) (VP (VBP start) (CC and) (VBP carry) (PP (IN on) (ADVP (RB spontaneously)))) (. .)))
Activation energy, which is defined as the amount of energy required to make the reaction start and carry on spontaneously.
(ROOT (S (NP (NP (DT The) (NN amount)) (PP (IN of) (NP (NP (NN energy)) (VP (VBN required) (S (VP (TO to) (VP (VB begin) (NP (DT a) (JJ chemical) (NN reaction))))))))) (VP (VBZ is) (VP (VBN known) (PP (IN as) (NP (DT the) (NN activation) (NN energy))))) (. .)))