Semantic roles, also known as theta roles or thematic roles, are a theoretical framework in linguistics that describes the relationship between the verb in a sentence and the nouns or noun phrases that it governs. These roles indicate the specific semantic or thematic relationship that each argument of a verb has with the action described by the verb. For example, in the sentence "John ate a sandwich," John is the agent, the one carrying out the action of eating, while the sandwich is the patient, the entity that undergoes the action. Semantic roles help to identify the various participants in a sentence and how they contribute to the overall meaning of the sentence. They are essential for understanding the syntactic structure and semantic interpretation of sentences. Research in semantic roles focuses on identifying and defining different types of roles, determining how they are assigned in different languages, and investigating their role in sentence processing and comprehension. Overall, semantic roles provide a crucial framework for understanding the relationships between verbs and their arguments in natural language.