sentences:  In certain syntactic environments (e.g.specifier VP and the specifier position of a TP which introduces a non-finite verb), case features are unable to be “checked”, and a determiner phrase must move throughout the phrase structure in order to check the case features.When this happens, a movement rule is initiated, and the structure is altered so that we hear the DP overtly pronounced in the position of the sentence which it has been moved to; a DP-trace is an empty category that appears at the original spot (the underlying position) of the DP, and stands for the syntactic space in the tree that the DP previously occupied.