Definition:Pentagram

Definition

A pentagram is a regular star polygon formed by the line segments connecting alternate vertices of a regular pentagon:

Also known as

In certain non-mathematical contexts, the words pentacle or pentangle are often seen for pentagram.

The word pentalpha is a $17$th century revival of another ancient Greek name for this shape, deriving from a construction from five overlapping $\Alpha$ (greek Alpha) symbols.

Also see

• Results about pentagrams can be found here.

Historical Note

The pentagram was known in ancient Babylonia.

It is believed to have been transported from there to ancient Greece, where it was revered by the Pythagoreans as a symbol of health.

Linguistic Note

The word pentagram derives from the Greek πεντάγραμμον (pentagrammon), from πέντε (pente), meaning five, and γραμμή (grammē), meaning line.

Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $1 \cdotp 61803 \, 39887 \, 49894 \, 84820 \, 45868 \, 34365 \, 63811 \, 77203 \, 09179 \, 80576 \ldots$
• 1989: Ephraim J. Borowski and Jonathan M. Borwein: Dictionary of Mathematics ... (previous) ... (next): pentagram, pentangle or pentacle
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $1 \cdotp 61803 \, 39887 \, 49894 \, 84820 \, 45868 \, 34365 \, 63811 \, 77203 \, 09179 \, 80576 \ldots$
• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): pentagram
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): pentagram
• 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): pentagram
• 2021: Richard Earl and James Nicholson: The Concise Oxford Dictionary of Mathematics (6th ed.) ... (previous) ... (next): pentagram