Formal Language Theory (Flt) Is an Important Part of the Mathematics of Computers And Contains an Extensive Corpus of Research Findings and Theorems on Rule-Based Generative Rule Systems (Grs). Format Language Theory (Flt) Has a Wide Range of Applications, Including Computer Programs, Music, Visual Patterns, Animal Vocalizations, Rna Structure, and Even Dance. In This Paper Discuss the Chomsky Hierarchy, Languages With a Slightly Sensitive Context, Cognitive Complexity, Languages Used In Subregular Conventions.