( ( ( ( The half-life ) ( of ( C 14 ) ) ) ( -LRB- ( ( that ( is ( ( the time ) ( ( ( required ( for ( a sample ) ) ) ( to decay ) ) ( to ( half ( its ( original amount ) ) ) ) ) ) ) ) -RRB- ) ) ) ( ( is ( known ( to ( be ( 5730 years ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NP (DT The) (NN half-life)) (PP (IN of) (NP (NNP C) (CD 14)))) (PRN (-LRB- -LRB-) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (NP (NP (DT the) (NN time)) (VP (VBN required) (PP (IN for) (NP (DT a) (NN sample))) (PP (TO to) (NP (NN decay))) (PP (TO to) (NP (PDT half) (PRP$ its) (JJ original) (NN amount)))))))) (-RRB- -RRB-))) (VP (VBZ is) (VP (VBN known) (S (VP (TO to) (VP (VB be) (NP (CD 5730) (NNS years))))))) (. .)))
The half-life of C 14 (that is the time required for a sample to decay to half its original amount) is known to be 5730 years.
(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)))))))))) (. .)))