Example: An active sentence into Passive sentence The rule relating active and passive sentences are given by Chomsky is NP1-Aux-V-NP2 -> NP2-Aux+be+en-V-by-NP1 This rule says that NP1-Aux-V-NP2 is replaced by NP2-Aux+be+en-V-by-NP1 Consider the active sentence “Police will catch the snatcher” The passive transformation rule will convert the sentence into: The + culprit+ will + be+ en + catch + by+ police