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In mathematical analysis, the word ''region'' usually refers to a subset of or that is open (in the standard Euclidean topology), connected and non-empty. A closed region is sometimes defined to be the closure of a region. Regions and closed regions are often used as domains of functions or differential equations. According to Kreyszig,〔Erwin Kreyszig (1993) ''Advanced Engineering Mathematics'', 7th edition, p. 720, John Wiley & Sons, ISBN 0-471-55380-8〕 :A region is a set consisting of a domain plus, perhaps, some or all of its boundary points. (The reader is warned that some authors use the term "region" for what we call a domain (standard terminology ), and others make no distinction between the two terms.) According to Yue Kuen Kwok, :An open connected set is called an ''open region'' or ''domain''. ...to an open region we may add none, some, or all its limit points, and simply call the new set a ''region''.〔Yue Kuen Kwok (2002) ''Applied Complex Variables for Scientists and Engineers'', § 1.4 Some topological definitions, p 23, Cambridge University Press, ISBN 0-521-00462-4〕 ==See also== * Jordan curve theorem * Riemann mapping theorem * Domain (mathematical analysis) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Region (mathematics)」の詳細全文を読む スポンサード リンク
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