( ( The half-life ) ( ( is ( ( the time ) ( ( ( required ( for ( one-half ( of ( ( the atoms ) ( of ( the isotope ) ) ) ) ) ) ) ( to decay ) ) ( into ( a ( different element ) ) ) ) ) ) . ) )
(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 one-half)) (PP (IN of) (NP (NP (DT the) (NNS atoms)) (PP (IN of) (NP (DT the) (NN isotope))))))) (PP (TO to) (NP (NN decay))) (PP (IN into) (NP (DT a) (JJ different) (NN element)))))) (. .)))
The half-life is the time required for one-half of the atoms of the isotope to decay into a different element.
(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)))))))))) (. .)))