( ( ( ( ( ( ( The rate ) ( of ( ( an ( isotope 's ) ) decay ) ) ) ( is ( defined ( by ( its half-life ) ) ) ) ) , ) or ) ( ( the time ) ( it ( takes ( for ( ( one half ) ( of ( ( a ( given amount ) ) ( of ( ( the element ) ( to decay ) ) ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (DT The) (NN rate)) (PP (IN of) (NP (NP (DT an) (NN isotope) (POS 's)) (NN decay)))) (VP (VBZ is) (VP (VBN defined) (PP (IN by) (NP (PRP$ its) (NN half-life)))))) (, ,) (CC or) (S (NP (DT the) (NN time)) (NP (PRP it)) (VP (VBZ takes) (PP (IN for) (NP (NP (CD one) (NN half)) (PP (IN of) (NP (NP (DT a) (VBN given) (NN amount)) (PP (IN of) (NP (NP (DT the) (NN element)) (PP (TO to) (NP (NN decay))))))))))) (. .)))
The rate of an isotope's decay is defined by its half-life, or the time it takes for one half of a given amount of the element 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))))))) (. .)))