This chapter examines the nature of semantic relations and their main applications in information science. The nature and types of semantic relations are discussed from the perspectives of linguistics and psychology. An overview of the semantic relations used in knowledge structures such as thesauri and ontologies are provided, as well as the main techniques used in the automatic extraction of semantic relations from text. The chapter then reviews the use of semantic relations in information

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... raction, information retrieval, question-answering and automatic text summarization applications. we might initially regard as basic and elemental are revealed upon further examination to involve internal structure, or in other words, internal relationships." (p. 3) Concepts and relations are often expressed in language and text. Language is used not just for communicating concepts and relations, but also for representing, storing and reasoning with concepts and relations. We shall examine the nature of semantic relations from a linguistic and psychological perspective, with an emphasis on relations expressed in text. The usefulness of semantic relations in information science, especially in ontology construction, information extraction, information retrieval, question-answering and text summarization is discussed. Research and development in information science have focused on concepts and terms, but the focus will increasingly shift to the identification, processing and management of relations to achieve greater effectiveness and refinement in information science techniques. Previous chapters in ARIST on natural language processing (Chowdhury, 2003) , text mining (Trybula, 1999), information retrieval and the philosophy of language (Blair, 2003) , and query expansion (Efthimiadis, 1996) provide a background for this discussion, as semantic relations are an important part of these applications.