( ( Half ( Life Half-life ) ) ( ( describes ( ( the time ) ( it ( takes ( for ( ( half ( the numbers ) ) ( of ( isotopes ( of ( an ( atom ( to ( undergo decay ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NN Half) (NNP Life) (NNP Half-life)) (VP (VBZ describes) (NP (NP (DT the) (NN time)) (SBAR (S (NP (PRP it)) (VP (VBZ takes) (PP (IN for) (NP (NP (PDT half) (DT the) (NNS numbers)) (PP (IN of) (NP (NP (NNS isotopes)) (PP (IN of) (NP (DT an) (NN atom) (S (VP (TO to) (VP (VB undergo) (NP (NN decay)))))))))))))))) (. .)))
Half Life Half-life describes the time it takes for half the numbers of isotopes of an atom to undergo decay.
(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)))))))))) (. .)))