( ( ( ( Formula Mass ) - ) ( ( the sum ) ( of ( ( atomic weights ) ( of ( ( the atoms ) ( in ( a molecule ) ) ) ) ) ) ) ) . )
(ROOT (NP (NP (NNP Formula) (NNP Mass)) (: -) (NP (NP (DT the) (NN sum)) (PP (IN of) (NP (NP (JJ atomic) (NNS weights)) (PP (IN of) (NP (NP (DT the) (NNS atoms)) (PP (IN in) (NP (DT a) (NN molecule)))))))) (. .)))
Formula Mass- the sum of atomic weights of the atoms in a molecule.
(ROOT (S (NP (NP (DT The) (NN sum)) (PP (IN of) (NP (NP (DT the) (NNS masses)) (PP (IN of) (NP (NP (DT the) (NNS atoms)) (PP (IN in) (NP (DT the) (NN formula)))))))) (VP (VBZ is) (VP (VBN referred) (PP (TO to) (NP (RB as) (JJ molecular) (NN mass))))) (. .)))