( ( The half-life ) ( ( is ( ( the time ) ( required ( for ( half ( of ( ( a ( given number ) ) ( of ( ( parent isotopes ) ( to ( decay ( to ( a ( daughter isotope ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN half-life)) (VP (VBZ is) (NP (NP (DT the) (NN time)) (VP (VBN required) (PP (IN for) (NP (NP (NN half)) (PP (IN of) (NP (NP (DT a) (VBN given) (NN number)) (PP (IN of) (NP (NP (NN parent) (NNS isotopes)) (PP (TO to) (NP (NP (NN decay)) (PP (TO to) (NP (DT a) (NN daughter) (NN isotope)))))))))))))) (. .)))
The half-life is the time required for half of a given number of parent isotopes to decay to a daughter isotope.
(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)))))))))) (. .)))