There-insertion

Definition
There-insertion is a operation which inserts expletive there in the first, presumably the subject position of an existential sentence.

Example
(i)a has been analyzed as being derived from (i)b by inserting there in the empty slot '__'.

(i) a there is someone in the room b  __ is someone in the room

This construction is now usually analyzed with the expletive base-generated in subject position and the logical subject adjoined or attached to VP. See CHAIN, Definiteness effect.

Links

 * Utrecht Lexicon of Linguistics