( Oxygen ( ( is ( ( the ( third-most ( common element ) ) ) ( by ( ( mass ( in ( the universe ) ) ) ( -LRB- ( ( although ( ( ( ( carbon forms ) more ) ( of ( the atoms ) ) ) ( it ( is ( a ( lighter atom ) ) ) ) ) ) -RRB- ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Oxygen)) (VP (VBZ is) (NP (NP (DT the) (JJ third-most) (JJ common) (NN element)) (PP (IN by) (NP (NP (NN mass)) (PP (IN in) (NP (DT the) (NN universe))) (PRN (-LRB- -LRB-) (SBAR (IN although) (S (PP (ADVP (NP (CD carbon) (NNS forms)) (RBR more)) (IN of) (NP (DT the) (NNS atoms))) (NP (PRP it)) (VP (VBZ is) (NP (DT a) (JJR lighter) (NN atom))))) (-RRB- -RRB-)))))) (. .)))
Oxygen is the third-most common element by mass in the universe (although carbon forms more of the atoms it is a lighter atom).
(ROOT (S (NP (NNP Carbon)) (VP (VBZ is) (NP (NP (DT the) (ADJP (RBS most) (VBN found)) (NN element)) (PP (IN in) (NP (VBG living) (NNS organisms))))) (. .)))