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An affix grammar is a kind of formal grammar; it is used to describe the syntax of languages, mainly computer languages, using an approach based on how natural language is typically described. The grammatical rules of an affix grammar are those of a context-free grammar, except that certain parts in the nonterminals (the affixes) are used as arguments. If the same affix occurs multiple times in a rule, its value must agree, i.e. it must be the same everywhere. In some types of affix grammar, more complex relationships between affix values are possible. == Example == We can describe an extremely simple fragment of English in the following manner: ''Sentence'' → ''Subject'' ''Predicate'' ''Subject'' → ''Noun'' ''Predicate'' → ''Verb'' ''Object'' ''Object'' → ''Noun'' ''Noun'' → John ''Noun'' → Mary ''Noun'' → children ''Noun'' → parents ''Verb'' → like ''Verb'' → likes ''Verb'' → help ''Verb'' → helps This context-free grammar describes simple sentences such as John likes children Mary helps John children help parents parents like John With more nouns and verbs, and more rules to introduce other parts of speech, a large range of English sentences can be described; so this is a promising approach for describing the syntax of English. However, the given grammar also describes sentences such as John like children children helps parents These sentences are wrong: in English, subject and verb have a grammatical number, which must agree. An affix grammar can express this directly: This grammar only describes correct English sentences, although it could be argued that John likes John is still incorrect and should instead read John likes himself This, too, can be incorporated using affixes, if the means of describing the relationships between different affix values are powerful enough. As remarked above, these means depend on the type of affix grammar chosen.. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Affix grammar」の詳細全文を読む スポンサード リンク
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