( ( ( The half-life ) ( of ( an isotope ) ) ) ( ( is ( ( the amount ) ( of ( time ( ( taken ( for ( half ( of ( the amount ) ) ) ) ) ( to decay ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN half-life)) (PP (IN of) (NP (DT an) (NN isotope)))) (VP (VBZ is) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NP (NN time)) (VP (VBN taken) (PP (IN for) (NP (NP (NN half)) (PP (IN of) (NP (DT the) (NN amount))))) (PP (TO to) (NP (NN decay)))))))) (. .)))
The half-life of an isotope is the amount of time taken for half of the amount 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)))))))))) (. .)))