Do not talk.
( ( ( Do not ) talk ) . )
(ROOT (S (VP (VB Do) (RB not) (VP (VB talk))) (. .)))
Don't speak until they all leave.
( ( ( Do n't ) ( speak ( until ( they ( all leave ) ) ) ) ) . )
(ROOT (S (VP (VB Do) (RB n't) (VP (VB speak) (SBAR (IN until) (S (NP (PRP they)) (RB all) (VP (VB leave)))))) (. .)))