( Reactivity ( ( is ( ( the ability ) ( of ( a ( substance ( to ( undergo ( ( a ( chemical reaction ) ) ( such ( as ( combining ( with ( another substance ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Reactivity)) (VP (VBZ is) (NP (NP (DT the) (NN ability)) (PP (IN of) (NP (DT a) (NN substance) (S (VP (TO to) (VP (VB undergo) (NP (NP (DT a) (JJ chemical) (NN reaction)) (PP (JJ such) (IN as) (S (VP (VBG combining) (PP (IN with) (NP (DT another) (NN substance)))))))))))))) (. .)))
Reactivity is the ability of a substance to undergo a chemical reaction such as combining with another substance.
(ROOT (S (NP (NP (DT The) (NN ability)) (PP (IN of) (NP (NN matter) (S (VP (TO to) (VP (VB combine) (ADVP (RB chemically)) (PP (IN with) (NP (JJ other) (NNS substances))))))))) (VP (VBZ is) (VP (VBN known) (PP (IN as) (NP (NN reactivity))))) (. .)))