( ( That animal ) ( ( is ( a ( social animal ) ) ) . ) )
(ROOT (S (NP (DT That) (NN animal)) (VP (VBZ is) (NP (DT a) (JJ social) (NN animal))) (. .)))
That animal is a social animal.
(ROOT (S (PP (IN For) (NP (JJ social) (NNS animals))) (, ,) (NP (NN communication)) (VP (VBZ essential)) (. .)))