PRO

In Chomskyan syntax, PRO (also called big PRO, to distinguish it from pro in speech) is a null noun phrase that occurs in a position where it does not get case (or gets null case). PRO's meaning is determined by control.

Example
PRO is posited in particular for the notional subject of infinitives:
 * Masha asked Jaime [PRO to help her].

Origin
PRO was introduced by Chomsky 1981.

Other languages
German PRO (de)