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pentagon

B2
Fairly common

Pronunciation

UK

  • /pˈɛntəɡən/

US

  • /ˈpɛnɪˌɡɑn/

Meanings

Noun

  1. a five-sided polygon

Proper-noun

  1. the U.S. Department of Defense or its military leadership, especially as represented by its headquarters

  2. the five-sided U.S. Department of Defense headquarters building in Arlington, Virginia

Beyond the definition

A pentagon is best known as the large, five-sided building in Arlington, Virginia, that serves as the headquarters of the U.S. Department of Defense, often called the Pentagon. But before it became a symbol of American power, it was already a geometric shape with five sides and five angles. You'll find this shape in nature, in architecture, and in everyday objects like some kinds of dice or the faces of certain crystals.

Think of it this way: "penta-" means five, as in "pentathlon," so a pentagon is simply a polygon with five sides and five angles. You might say, "The architect designed the gazebo with a pentagonal base." Or, using its more famous meaning: "News reports focused on security measures at the Pentagon after the incident."

Examples

  1. 1

    Basic shape

    The children drew a pentagon next to the square and the triangle.

  2. 2

    Geometry

    In a regular pentagon, all the sides are the same length.

    • Phraseregular pentagon

      a pentagon with equal sides and equal angles

  3. 3

    Visual design

    The logo uses three small pentagons arranged in a circle.

  4. 4

    U.S. government

    Officials at the Pentagon said the policy would change next year.

See also

Similar

  • five-sided polygon
  • five-sided shape

Contrast

Do not confuse

  • pentagram

Used with (collocations)

  • regular pentagon
  • irregular pentagon
  • sides of a pentagon

Word family

Explore

Forms and spellings

2 forms open this card.

Main spelling

  • pentagonnoun

Forms

  • pentagonspluralnoun