This article presents a brief history of the term “information” and its different meanings, which are both important and difficult because the different meanings of the term imply whole theories of knowledge. The article further considers the relation between “information” and the concepts “matter and energy”, “data”, “sign and meaning”, “knowledge” and “communication”. It presents and analyses the influence of information in information studies and knowledge organization and contains a presentation and critical analysis of some compound terms such as “information need”, “information overload” and “information retrieval”, which illuminate the use of the term information in information studies. An appendix provides a chronological list of definitions of information.