( ( Carbon-14 ( ( A ( radioactive isotope ) ) ( of carbon ) ) ) . )
(ROOT (S (VP (VB Carbon-14) (NP (NP (DT A) (JJ radioactive) (NN isotope)) (PP (IN of) (NP (NN carbon))))) (. .)))
Carbon-14 A radioactive isotope of carbon.
(ROOT (S (NP (NP (NNP Carbon) (CD 14) (NN isotope)) (PP (IN of) (NP (NN carbon)))) (VP (VBZ is) (ADVP (RB typically)) (VP (VBN used) (PP (TO to) (NP (NN date) (JJ ancient) (NNS items))))) (. .)))