( ( ( ( Examples ( of ( the ( three ( main ( galaxy types ) ) ) ) ) ) , ) ( based ( on ( their ( optical spectra ) ) ) ) ) ; )
(ROOT (NP (NP (NP (NNS Examples)) (PP (IN of) (NP (DT the) (CD three) (JJ main) (NN galaxy) (NNS types))) (, ,) (VP (VBN based) (PP (IN on) (NP (PRP$ their) (JJ optical) (NN spectra))))) (: ;)))
Examples of the three main galaxy types, based on their optical spectra;
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD three) (NNS types)) (PP (IN of) (NP (NNS galaxies))))) (. .)))