填空题

It has been perceived that languages tend to be organized around
grammatical categories such as noun and verb, nominative and accusative,
or present and past. The grammar of language is organized around such 41. ______
fundamental categories, though many languages express the relationships
between words and syntax in the other discrete ways. 42. ______
In addition to make substantial use of discrete categories, language 43. ______
has the important property that organizes elements into recursive structures; 44. ______
which allows, for example, a noun phrase to contain another noun phrase (as in 45. ______
"the chimpanzee’s lips") or a clause to contain a clause (as in "I think that it’s raining").
Because recursion in grammar was implicitly recognized much earlier, 46. ______
the importance of this aspect of language became more popular after the 1957
publication of Noam Chomsky’s book Syntactic Structures, which presents a 47. ______
formal grammar of a fragment of English. Prior to this, the most detail 48. ______
descriptions of linguistic systems were of phonological or morphological systems.
Chomsky used a context-free grammar augment with transformations. 49. ______
Since then, following the trend of Chomskyan linguistics, context-free grammars
have written for substantial fragments of various languages. It has been 50. ______
demonstrated, however, that human languages include cross-serial dependencies,
which cannot be handled adequately by context-free grammars.