If all the production rules have single non-terminal symbol on the left side,…

Answer: Context-free grammar. A grammar where every production has a single non-terminal on the left-hand side is called a context-free grammar.

• Formal definition: Each production has the form A -> α, where A is a single non-terminal and α is any string of terminals and/or non-terminals.

• Example: S -> aSb | ε generates balanced strings of a's and b's and shows a typical context-free production pattern.

• Why other classes do not match:

• Context-sensitive grammars: Left sides can include surrounding context (e.g., αAβ -> αγβ) and productions typically must not decrease string length; the left side is not restricted to a single non-terminal.

• Unrestricted or phrase-structure grammars: No restriction on the left-hand side; they are the most general class and do not require a single non-terminal on the left.