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pentagram
ˈpɛntəɡram/

noun

a five-pointed star that is formed by drawing a continuous line in five straight segments, often used as a mystic and magical symbol.

A pentagram (sometimes known as a pentalpha or pentangle or a star pentagon) is the shape of a five-pointed star drawn with five straight strokes.

The word pentagram comes from the Greek word πενÏ,,άγραμμον (pentagrammon), from πένÏ,,ε (pente), "five" + γραμμή (grammÄ"), "line".

The word "pentacle" is sometimes used synonymously with "pentagram".

The word pentalpha is a learned modern (17th-century) revival of a post-classical Greek name of the shape.(wikipedia)


A regular pentagram

Geometry


A regular pentagram colored to distinguish its line segments of different lengths. The four lengths are in golden ratio to one another.

The pentagram is the simplest regular star polygon. The pentagram contains ten points (the five points of the star, and the five vertices of the inner pentagon) and fifteen line segments. It is represented by the Schläfli symbol {5/2}. Like a regular pentagon, and a regular pentagon with a pentagram constructed inside it, the regular pentagram has as its symmetry group the dihedral group of order 10.