Description: Some concept of Automata and Complexity Theory are Administrivia, Closure Properties, Context-Free Grammars, Decision Properties, Deterministic Finite Automata, Intractable Problems, More Undecidable Problems. Main points of this lecture are: Regular Expressions Three, Practical Applications, Mathematics, Phenomenon Discovered, Definitional Power, Regular Languages, Formally Defined, Language, Induction, Regular Language