( ( ( The ( combined number ) ) ( of ( ( protons and ) neutrons ) ) ) ( ( is ( ( called ( the ( atomic ( mass number ) ) ) ) ( -LRB- ( ( symbol ( is A ) ) -RRB- ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (VBN combined) (NN number)) (PP (IN of) (NP (NNS protons) (CC and) (NNS neutrons)))) (VP (VBZ is) (VP (VBN called) (NP (DT the) (JJ atomic) (NN mass) (NN number)) (PRN (-LRB- -LRB-) (S (NP (NN symbol)) (VP (VBZ is) (NP (NNP A)))) (-RRB- -RRB-)))) (. .)))
The combined number of protons and neutrons is called the atomic mass number (symbol is A).
(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)))))) (. .)))