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A heptagram, septagram, or septegram is a seven-pointed star drawn with seven straight strokes. The name heptagram combines a numeral prefix, ''hepta-'', with the Greek suffix ''-gram''. The ''-gram'' suffix derives from ''γραμμῆς'' (''grammēs'') meaning a line.〔(γραμμή ), Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus〕 ==Geometry== In general, a heptagram is any self-intersecting heptagon (7-sided polygon). There are two ''regular'' heptagrams, labeled as and , with the second number representing the vertex interval step from a regular heptagon, . This is the smallest star polygon that can be drawn in two forms, as irreducible fractions. The two heptagrams are sometimes called the ''heptagram'' (for ) and the ''great heptagram'' (for ). The previous one, the regular hexagram , is a compound of two triangles. The smallest star polygon is the pentagram. The next one is the octagram, followed by the regular enneagram, which also has two forms: and , as well as one compound of 3 triangles . | ++ |- align=center | 7-2 prism | 7-3 prism |80px Complete graph |- align=center |80px 7-2 antiprism |80px 7-3 antiprism |80px 7-4 antiprism |} 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「heptagram」の詳細全文を読む スポンサード リンク
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