In context-free grammar derivations, what is a 'Sentential Form'?
A sentential form is any intermediate string $\alpha ∈ (V ∪ T)* generated during grammatical derivations$ from S.
What is a 'Sentence' generated by a Context-Free Grammar?
A sentence is a fully derived terminal string belonging to language L(G).
What is the yield of a parse tree?
Concatenating leaf labels left-to-right recovers the derived sentence yield.
If a CFG rule contains A → A $\alpha (where non-terminal A appears as$ the FIRST symbol on RHS), what type of recursion is present?
Direct appearance of A as the leftmost symbol in its own rule RHS (A → A $\alpha ) constitutes immediate left recursion$.
If a CFG contains rules A → B $\alpha$ and B → A $\beta , what type of recursion$ is present?
Indirect left recursion occurs when A derives a sentential form starting with A through a multi-step chain A ⇒+ A $\gamma$.