Thematic relations

In linguistics, thematic relations is a term used within certain theories to express the role that a noun phrase plays with respect to the action or state described by a governing verb, commonly the sentence's main verb. For example, in the sentence "Susan ate an apple", Susan is the doer of the eating, so she is an agent; the apple is the item that is eaten, so it is a patient. While most modern linguistic theories make reference to such relations in one form or another, the general term, as well as the terms for specific relations, varies: 'participant role', 'semantic role', and 'deep case' have also been employed with similar sense.

Here is a list of the major thematic relations.

There are no clear boundaries between these relations. For example, in "the hammer broke the window", some linguists treat the hammer as an agent and others as an instrument, while yet others regard it as having a special role different from these.

In many languages, such as Finnish and Hungarian and Turkish, thematic relations may be reflected in the case-marking on the noun. For instance, Hungarian has an instrumental case ending, (-val/-vel) which explicitly marks the instrument of a sentence. Languages like English often mark such thematic relations with prepositions.

The term "thematic relation" is frequently confused with theta role. Many linguists (particularly generative grammarians) use the terms interchangeably. This is because theta roles are typically named by the most prominent thematic relation that they are associated with. To make matters more confusing, depending upon which theoretical approach one assumes, the grammatical relations of subject and object, etc., are often closely tied to the semantic relations. For example, in the typological tradition agents/actors are tied closely to the notion of subject (S). Here is a way to distinguish these ideas, when they are used distinctly:

...
Wikipedia