What does pentagon mean?
A pentagon is a polygon with five straight sides and five angles. In geometry, the term can refer to any five-sided figure, although “regular pentagon” specifically describes one with equal sides and equal angles. Pentagons are less common in everyday design than triangles, squares, and rectangles, but they appear in architecture, symbols, and objects whose form is deliberately distinctive. In American English, “the Pentagon” is also the conventional name for the headquarters of the US Department of Defense in Arlington, Virginia, making the word an important cultural and political reference as well as a mathematical term. The word comes from Greek roots meaning “five” and “angle,” which makes its meaning relatively transparent.
A polygon with five sides and five angles.
"The logo incorporates a stylized pentagon."
The Pentagon, the headquarters of the US Department of Defense.
"The Pentagon released a statement following the meeting."
The regular plural is “pentagons.” When referring to the US Department of Defense headquarters, “the Pentagon” is normally used as a singular proper noun.
"Several pentagons were drawn on the whiteboard."
A pentagon is the simplest polygon that can be divided into a pentagram, the five-pointed star familiar from ancient symbols and modern design.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does pentagon come from?
“Pentagon” comes from the Greek pente, meaning “five,” and gonia, meaning “angle.” The form entered English through Latin and was used in mathematical and architectural contexts. Its relatives include “pentagram,” “pentathlon,” and “pentagonal,” all built on the same Greek numerical and geometric elements.
Related word forms
How pentagon is actually used
In general use, “pentagon” is a common noun and is usually written with a lowercase initial letter. The building and the US Department of Defense are usually referred to as “the Pentagon,” with a capital P.
Easily confused with pentagon
A pentagon is a five-sided geometric figure, whereas a pentagram is a five-pointed star formed by intersecting lines.