||Two or more clauses constitute a discourse. A discourse is typically coherent: the clauses are organized in a principled way, as opposed to disconnected. Theories of discourse structure explain what such coherence consists in. There are two popular theories. Question-based theories maintain that discourses are structured as question-answer exchanges Relations-based theories maintain that discourses are structured by coherence relations. Relations-based theories disagree over the number of coherence relations, and what constraints there are for where a relation can attach to the preceding discourse (e.g. the right frontier constraint). Discourse coherence has been argued to play a prominent role in various disputes in semantics and pragmatics. Examples include how context-sensitivity is resolved, how pragmatic inferences are derived, and even the distinction between lying and misleading.