Theta Roles

A theta role is a bundle of thematic relations associated with a particular argument. It's not a thematic relation, but a group of them.


Thematic Relations

We can use thematic relations to encode the semantic relation between the argument and the predicate, allowing us to show selectional restrictions.

  • Agent: initiator of the action, capable of volition
    • Brad hit Andrew
  • Natural Phenomenon: initiator of the action, incapable of volition
    • A falling rock hit Terry
  • Experiencer: argument that experiences or perceives the event.
    • Becki saw the Eclipse
    • A falling rock hit Terry
  • Theme/Patient/Percept: entity that undergoes actions, or is moved, experienced or perceived
    • Susan loves cookies
    • A falling rock hit Terry
    • The syntactician bought a phonology textbook
  • Goal: The entity towards which motion takes place (may involve abstract motion).
    • Millie went to Chicago
    • Travis was given a semantics article
    • A falling rock hit Terry
  • Recipient: A special kind of goal that involves a change of possession
    • Julie gave Jessica the book
    • Roy received a scolding from Sherilyn
  • Source: The opposite of goal, entity from which movement occurs
    • Bob gave Steve the syntax assignment
    • Stacy came from class
  • Location: Place where action occurs
    • Andrew is in Tucson's finest apartment
    • We're all at school
  • Instrument: The entity with which action occurs.
    • Patrick hacked the computer apart with an axe
    • This key will open the door to the linguistics building
  • Beneficiary: The entity for whom the action occurs
    • He bought these flowers for Jason
    • She cooked Matt dinner
  • Expletives/Pleonastics: An NP without a Theta Role (and hence without a thematic relation)
    • It rained
    • It is likely that Bob left

Theta Grids

A theta grid for a verb lists the theta roles required for it (i.e. the arguments it needs) and the indice in the sentence:


(The indices are of course different from the binding theory ones).

Adjuncts are not included in theta grids, as they are optional rather than obligatory.

Theta Criterion

A sentence meets the theta criterion iff each argument has only one theta role (by definition…) and each theta role is assigned to only one argument (also by definition).


The subject is the external theta role, and each argument is the internal theta role.

The Extended Projection Principle (EPP)

There is a rule (in English) that every sentence must have a subject. The EPP is an attempt to redefine the problem and acknowledge it - it doesn't account for it. However, we still use it where we must.

So the sentence 'rained' meets the theta criterion (doesn't take any theta roles), but violates the EPP (no subject).

Hence the Rule of Expletive Insertion says to insert 'it' into the subject position.