( ( ( The time ) ( ( required ( for ( half ( of ( the atoms ) ) ) ) ) ( in ( ( any ( given quantity ) ) ( of ( ( a ( radioactive isotope ) ) ( to decay ) ) ) ) ) ) ) ( ( is ( ( the half-life ) ( of ( that isotope ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN time)) (VP (VBN required) (PP (IN for) (NP (NP (NN half)) (PP (IN of) (NP (DT the) (NNS atoms))))) (PP (IN in) (NP (NP (DT any) (VBN given) (NN quantity)) (PP (IN of) (NP (NP (DT a) (JJ radioactive) (NN isotope)) (PP (TO to) (NP (NN decay))))))))) (VP (VBZ is) (NP (NP (DT the) (NN half-life)) (PP (IN of) (NP (DT that) (NN isotope))))) (. .)))
The time required for half of the atoms in any given quantity of a radioactive isotope to decay is the half-life of that 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)))))))))) (. .)))