( ( ( Mass number ) ( ( The number ) ( of ( ( nucleons ( -LRB- ( ( ( neutrons and ) protons ) -RRB- ) ) ) ( in ( ( the nucleus ) ( of ( an atom ) ) ) ) ) ) ) ) . )
(ROOT (NP (NP (NNP Mass) (NN number)) (NP (NP (DT The) (NN number)) (PP (IN of) (NP (NP (NP (NNS nucleons)) (PRN (-LRB- -LRB-) (NP (NP (NNS neutrons)) (CC and) (NP (NNS protons))) (-RRB- -RRB-))) (PP (IN in) (NP (NP (DT the) (NN nucleus)) (PP (IN of) (NP (DT an) (NN atom)))))))) (. .)))
Mass number The number of nucleons (neutrons and protons) 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))))) (. .)))