( ( The half-life ) ( ( is ( ( ( the amount ) ( of time ) ) ( it ( ( takes ( for ( ( one half ) ( of ( ( the ( initial amount ) ) ( of ( ( ( ( the parent ) , ) ( radioactive isotope ) ) , ) ) ) ) ) ) ) ( to ( decay ( to ( the ( daughter isotope ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN half-life)) (VP (VBZ is) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NN time))) (SBAR (S (NP (PRP it)) (VP (VBZ takes) (PP (IN for) (NP (NP (CD one) (NN half)) (PP (IN of) (NP (NP (DT the) (JJ initial) (NN amount)) (PP (IN of) (NP (NP (DT the) (NN parent)) (, ,) (NP (JJ radioactive) (NN isotope)) (, ,))))))) (PP (TO to) (NP (NP (NN decay)) (PP (TO to) (NP (DT the) (NN daughter) (NN isotope)))))))))) (. .)))
The half-life is the amount of time it takes for one half of the initial amount of the parent, radioactive isotope, to decay to the 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)))))))))) (. .)))