( ( ( ( ( ( ( The rate ) ( of ( this decay ) ) ) ( is ( measured ( in half-lives ) ) ) ) , ) or ) ( ( the time ) ( it ( ( takes ( half ( of ( the ( radioactive atoms ) ) ) ) ) ( to decay ) ) ) ) ) . )
(ROOT (S (S (NP (NP (DT The) (NN rate)) (PP (IN of) (NP (DT this) (NN decay)))) (VP (VBZ is) (VP (VBN measured) (PP (IN in) (NP (NNS half-lives)))))) (, ,) (CC or) (S (NP (DT the) (NN time)) (NP (PRP it)) (VP (VBZ takes) (NP (NP (NN half)) (PP (IN of) (NP (DT the) (JJ radioactive) (NNS atoms)))) (PP (TO to) (NP (NN decay))))) (. .)))
The rate of this decay is measured in half-lives, or the time it takes half of the radioactive atoms to decay.
(ROOT (S (NP (DT The) (NN decay) (NN rate)) (VP (VBZ is) (VP (VBN measured) (PP (IN in) (NP (NP (DT a) (NN unit)) (VP (VBN called) (NP (DT the) (NN half-life))))))) (. .)))