( They ( ( ( ( are herbivores ) , ) ( meaning ( they ( ( will only ) ( eat plants ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP are) (ADJP (JJ herbivores)) (, ,) (S (VP (VBG meaning) (SBAR (S (NP (PRP they)) (VP (MD will) (ADVP (RB only)) (VP (VB eat) (NP (NNS plants))))))))) (. .)))
They are herbivores, meaning they will only eat plants.
(ROOT (S (NP (NNS Herbivores)) (VP (VBP are) (NP (NP (NNS heterotrophs)) (SBAR (WHNP (WDT that)) (S (VP (VBP eat) (NP (UCP (ADJP (JJ only)) (CC or) (ADVP (RB mainly))) (NNS plants))))))) (. .)))