( ( ( The half-life ) ( of ( a ( radioactive substance ) ) ) ) ( ( is ( ( the amount ) ( of ( time ( ( required ( for ( half ( of a ) ) ) ) ( ( give sample ) ( to decay ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN half-life)) (PP (IN of) (NP (DT a) (JJ radioactive) (NN substance)))) (VP (VBZ is) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN time)) (VP (VBN required) (PP (IN for) (NP (QP (RB half) (IN of) (DT a)))) (S (VP (VB give) (NP (NN sample)) (PP (TO to) (NP (NN decay)))))))))) (. .)))
The half-life of a radioactive substance is the amount of time required for half of a give sample to decay.
(ROOT (S (NP (DT The) (NN term) (NN half-life)) (VP (VBZ decribes) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN time)) (VP (VBN required) (PP (IN for) (NP (NP (NN half)) (PP (IN of) (NP (DT the) (JJ original) (NN material))))) (PP (TO to) (NP (NP (NN decay)) (PP (IN in) (NP (DT an) (NN isotope)))))))))) (. .)))