Theta-role

Definition
Theta-role is the semantic relationship of an argument with the predicate it is an argument of is expressed through the assignment of a role by the predicate to the argument, in conformity with the theta criterion. Different theta-roles have different labels, such as Agent and Theme.

Example
In Ken sent me the argument Ken is the Agent of the predicate sent me, and the argument me is the Theme of the predicate sent. Other theta-roles that have been distinguished are Goal, Source, Experiencer.

Links

 * Utrecht Lexicon of Linguistics