Optional Transformation

非强制性转换

The term refers to one of two types of rule postulated by Noam Chomsky in his book Syntactic Structures, the other being obligatory.

Optional transformations may apply at a certain stage in a derivation; but it is not essential for the well-formedness of the sentence that they do so, e.g. the transformation from positive to negative, active to passive, or declarative to interrogative.

诺姆·乔姆斯基在其《句法结构》一书中假设的两类转换规则之一，另一类是强制性转换规则。非强制性转换可应用于派生过程的某一阶段，但本质上不是为了句子的合式性才应用这种转换，例如肯定句到被动句的转换，主动句到被动句的转换，陈述句到疑问句的转换。