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2. Context-free grammar - Wikipedia

   en.wikipedia.org/wiki/Context-free_grammar

   An extended context-free grammar (or regular right part grammar) is one in which the right-hand side of the production rules is allowed to be a regular expression over the grammar's terminals and nonterminals. Extended context-free grammars describe exactly the context-free languages.

3. Terminal and nonterminal symbols - Wikipedia

   en.wikipedia.org/wiki/Terminal_and_nonterminal...

   In fact, the language defined by a grammar is precisely the set of terminal strings that can be so derived. Context-free grammars are those grammars in which the left-hand side of each production rule consists of only a single nonterminal symbol. This restriction is non-trivial; not all languages can be generated by context-free grammars.

4. Chomsky normal form - Wikipedia

   en.wikipedia.org/wiki/Chomsky_normal_form

   By deleting in this grammar each ε-rule, unless its left-hand side is the start symbol, the transformed grammar is obtained. [4]: 90 For example, in the following grammar, with start symbol S 0, S 0 → AbB | C B → AA | AC C → b | c A → a | ε. the nonterminal A, and hence also B, is nullable, while neither C nor S 0 is.

5. Greibach normal form - Wikipedia

   en.wikipedia.org/wiki/Greibach_normal_form

   Some do not permit the second form of rule and cannot transform context-free grammars that can generate the empty word. For one such construction the size of the constructed grammar is O(n 4) in the general case and O(n 3) if no derivation of the original grammar consists of a single nonterminal symbol, where n is the size of the original ...

6. Node (linguistics) - Wikipedia

   en.wikipedia.org/wiki/Node_(linguistics)

   VP → V NP AdvP (studies linguistics enthusiastically) With a tree diagram, the sentence's structure can be depicted as in Figure 1. Figure 1. All the points illustrated by circles and diamonds are nodes in Figure 1, and the former are called nonterminal nodes and the latter terminal nodes. [2]

7. Noncontracting grammar - Wikipedia

   en.wikipedia.org/wiki/Noncontracting_grammar

   A context-sensitive grammar is a noncontracting grammar in which all rules are of the form αAβ → αγβ, where A is a nonterminal, and γ is a nonempty string of nonterminal and/or terminal symbols. However, some authors use the term context-sensitive grammar to refer to noncontracting grammars in general. [1]