Question: dcfl are not closed under?
Answer: DCFL = {L(M) : M is a DPDA}, where DCFL is the set of deterministic context free languages and DPDA stands for deterministic pushdown automaton. Here are some facts about DCFL: ... 2) DCFL is not closed under union, and not closed under intersection. 3) Both CFL and DCFL are closed under intersection with regular sets.