( ( The ( atomic ( mass number ) ) ) ( ( is ( ( ( the number ) ( of ( ( protons plus ) neutrons ) ) ) ( in ( the nucleus ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ atomic) (NN mass) (NN number)) (VP (VBZ is) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NNS protons) (CC plus) (NNS neutrons))) (PP (IN in) (NP (DT the) (NN nucleus))))) (. .)))
The atomic mass number is the number of protons plus neutrons in the nucleus.
(ROOT (S (S (S (VP (VBG Adding) (NP (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NNS protons)))) (CC plus) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NP (NNS neutrons)) (PP (IN in) (NP (DT an) (NN atom))))))))) (VP (VBZ decides) (NP (PRP$ its) (JJ approximate) (NN mass)))) (: ;) (S (NP (JJ atomic) (NN number)) (VP (VBZ is) (NP (NP (DT another) (NN word)) (PP (IN for) (NP (DT this) (NN value)))))) (. .)))