Tough Movement

tough移位

A term used in transformational grammar, referring to a rule which involves moving a noun phrase out of the predicate of a complement sentence. Sentences such as The ball was easy for John to catch were said to be derived by tough movement from the structure _NP[it _S[for John to catch the ball]_S ]_NP was easy, via a rule which extraposes the complement (it was easy for John to catch the ball). The rule of tough movement took the non-subject noun phrase from the extraposed complement (i.e. the ball) and substituted it for the initial subject pronoun of the sentence as a whole (i.e. it). 

转换语法术语，指将一个名词短语从一个补语句子的谓语中移出的规则。像The ball was easy for John to catch“此球易为约翰所接”这类句子被认为是通过tough移位从结构[it [for John to catch the ball] ]was easy派生而来，即通过一条补语外置的规则（it was easy for John to catch the ball“要约翰接此球很容易”）。tough移位规则将外置补语中的非主语名词短语（即the ball“此球”）移出并用来替换整个句子开头的主语代名词（即it）。