The Early Theory Of Chomsky

Phrase Rules Structure• Phrase-structure rules are a way to describe a given language

• S=> NP VP ; NP => Det + N1 ; N1 => AP N1 PP

• The first rule reads: An S (sentence) consists of an NP (noun phrase) followed by a VP (verb phrase). The second rule reads: A noun phrase consists of a Det (determiner) followed by an N (noun). Some further categories are listed here: AP (adjective phrase), AdvP (adverb phrase), PP (prepositional phrase), etc. Applying the phrase structure rules in a neutral manner, it is possible to generate many proper sentences of English. But it is also quite possible that the rules generate syntactically correct but semantically nonsensical sentences. The following example sentence is notorious in this regard, since it is complete nonsense, even though it is syntactically correct:

• Colorless green ideas sleep furiously

• This sentence was constructed by Noam Chomsky as an illustration that phrase structure rules are capable of generating

• syntactically correct but semantically incorrect sentences. Phrase structure rules break sentences down into their constituent parts. These constituents are often represented as tree structures. The tree for Chomsky's famous sentence can be rendered as follows:

• A constituent is any word or combination of words that is dominated by a single node. Thus each individual word is a constituent. Further, the subject NP Colorless green ideas, the minor NP green ideas, and the VP sleep furiously are constituents. Phrase structure rules and the tree structures that are associated with them are a form of immediate constituent analysis.

Transformational Grammar • In linguistics, a transformational grammar or transformational-generative

grammar (TGG) is a generative grammar, especially of a natural language, that has been developed in the Chomskyan tradition of phrase structure grammars (as opposed to dependency grammars). Additionally, transformational grammar is the tradition that gives rise to specific transformational grammars.

• In 1957, Noam Chomsky published Syntactic Structures, in which he developed the idea that each sentence in a language has two levels of representation — a deep structure and a surface structure. The deep structure represented the core semantic relations of a sentence, and was mapped on to the surface structure (which followed the phonological form of the sentence very closely) via transformations. Chomsky believed there are considerable similarities between languages' deep structures, and that these structures reveal properties, common to all languages that surface structures conceal. However, this may not have been the central motivation for introducing deep structure.

• Transformations had been proposed prior to the development of deep structure as a means of increasing the mathematical and descriptive power of context-free grammars. Similarly, deep structure was devised largely for technical reasons relating to early semantic theory.

• Generative grammar refers to a particular approach to the study of syntax. A generative grammar of a language attempts to give a set of rules that will correctly predict which combinations of words will form grammatical sentences. In most approaches to generative grammar, the rules will also predict the morphology of a sentence.

• Generative grammar originates in the work of Noam Chomsky, beginning in the late 1950s. Early versions of Chomsky's theory were called transformational grammar, and this term is still used as a collective term that includes his subsequent theories. There are a number of competing versions of generative grammar currently practiced within linguistics. Most versions of generative grammar characterize sentences as either grammatically correct (also known as well formed) or not. The rules of a generative grammar typically function as an algorithm to predict grammaticality as a discrete (yes-or-no) result.

• Morphophonology (also morphophonemics, morphonology) is a branch of linguistics which studies the interaction between morphological and phonological or phonetic processes. Its chief focus is the sound changes that take place in morphemes (minimal meaningful units) when they combine to form words.

• Morphophonological analysis often involves an attempt to give a series of formal rules that successfully predict the regular sound changes occurring in the morphemes of a given language. Such a series of rules converts a theoretical underlying representation into a surface form that is actually heard. The units of which the underlying representations of morphemes are composed are sometimes called morphophonemes. The surface form produced by the morphophonological rules may consist of phonemes (which are then subject to ordinary phonological rules to produce speech sounds or phones), or else the morphophonological analysis may bypass the phoneme stage and produce the phones itself.

morphophonemic

• When morphemes combine, they influence each other's sound structure (whether analyzed at a phonetic or phonemic level), resulting in different variant pronunciations for the same morpheme. Morphophonology attempts to analyze these processes. A language's morphophonological structure is generally described with a series of rules which, ideally, can predict every morphophonological alternation that takes place in the language.

• An example of a morphophonological alternation in English is provided by the plural morpheme, written as "-s" or "-es". Its pronunciation alternates between [s], [z], and [ɪz], as in cats, dogs, and horses respectively. A purely phonological analysis would likely assign to these three endings the phonemic representations /s/, /z/, /ɪz/. On a morphophonological level, however, they may all be considered to be forms of the underlying object //z//, which is a morphophonemic. The different forms it takes are dependent on the segment at the end of the morpheme to which it attaches – these dependencies are described by morphophonological rules. (The behaviour of the English past tense ending "-ed" is similar – it can be pronounced [t], [d] or [ɪd], as in hoped, bobbed and added.)