Formal grammars (Type 0, 1, 2, 3 — Chomsky hierarchy)

Regular languages & expressions

Finite-State Automata (FSA)

Finite-State Transducers (FST)

Context-Free Grammars (CFG)

Pushdown Automata (PDA)

Context-Sensitive Grammars

Turing Machines (concept)

Decidability & computational limits

Relation to linguistic levels