In certain theories of linguistics, thematic relations, also known as semantic roles, are the various roles that a noun phrase may play 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 modernlinguistic 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.
Major thematic relations
The following major thematic relations have been identified:
There are not always clear boundaries between these relations. For example, in "the hammer broke the window", hammer might be labeled an agent, an instrument, a force, or possibly a cause. Nevertheless, some thematic relation labels are more logically plausible than others.
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, which explicitly marks the instrument of a sentence. Languages like English often mark such thematic relations with prepositions.
Conflicting terminologies
The term thematic relation is frequently confused with theta role. Many linguists 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 frequently overlap with the notion of subject. These ideas, when they are used distinctly, can be distinguished as follows: ; Thematic relations ; Theta roles ; Grammatical relations Thematic relations concern the nature of the relationship between the meaning of the verb and the meaning of the noun. Theta roles are about the number of arguments that a verb requires. Theta roles are syntactic relations that refers to the semantic thematic relations. For example, take the sentence "Reggie gave the kibble to Fergus on Friday."
Thematic relations: Reggie is doing the action so is the agent, but he is also the source of the kibble ; the kibble is the entity acted upon so it is the patient; Fergus is the direction/goal or recipient of the giving. Friday represents the time of the action.
theta roles: The verb give requires three arguments. In generative grammar, this is encoded in terms of the number and type of theta roles the verb takes. The theta role is named by the most prominent thematic relation associated with it. So the three required arguments bear the theta roles named the agent the patient , and goal/recipient. On Friday does not receive a theta role from the verb, because it is an adjunct. Note that Reggie bears two thematic relations, but only one theta role.
grammatical relations: The subject of this sentence is Reggie, the object is the kibble, the indirect object is to Fergus, and on Friday is an oblique.
