( ( atomic mass ) ( Originally ( ( ( defined ( as ( ( the number ) ( of ( ( protons and ) neutrons ) ) ) ) ) ( in ( ( the nucleus ) ( of ( an atom ) ) ) ) ) . ) ) )
(ROOT (S (NP (JJ atomic) (NN mass)) (ADVP (RB Originally)) (VP (VBD defined) (PP (IN as) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NNS protons) (CC and) (NNS neutrons))))) (PP (IN in) (NP (NP (DT the) (NN nucleus)) (PP (IN of) (NP (DT an) (NN atom)))))) (. .)))
atomic mass Originally defined as the number of protons and neutrons in the nucleus of an atom.
(ROOT (S (NP (NP (DT The) (NN mass)) (PP (IN of) (NP (NNS atoms)))) (VP (VBZ is) (VP (VBN based) (PP (IN on) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NNS protons) (CC and) (NNS neutrons))))) (PP (IN in) (NP (NN nucleus))))) (. .)))