pentagon

Meanings

1. 1nouncountablemathematics

   A flat shape with five straight sides and five angles.

   Grammar: A regular pentagon has five equal sides.

   Patterns

   • draw a pentagon
   • a regular pentagon

   The students drew a pentagon on graph paper.

   Each side of a regular pentagon has the same length.

   The garden bed was laid out in the shape of a pentagon.

2. 2proper nounproperAmerican

   The headquarters of the U.S. Department of Defense, a large five-sided building near Washington, D.C.; also used for the American military leadership.

   Grammar: Capitalized and usually used with the: the Pentagon announced a new plan.

   Patterns

   • the Pentagon announced something
   • a Pentagon spokesman

   The Pentagon announced a review of its budget.

   A Pentagon official briefed reporters on Tuesday.

   Tourists took photographs of the Pentagon from across the river.

Word forms

Common combinations

regular pentagon

A regular pentagon has five equal sides.

draw a pentagon

Draw a pentagon and mark each angle.

the Pentagon announced

The Pentagon announced it would reduce the number of troops.

Pentagon officials

Pentagon officials declined to comment.

Pentagon spokesman

A Pentagon spokesman said the report was under review.

Synonyms and how they differ

five-sided figure

Five-sided figure is a plain description and is less technical than pentagon.

polygon

Polygon is a wider term for any flat shape with straight sides, and a pentagon is one type.

Defense Department

Defense Department is the formal name of the organization, while the Pentagon is a shorthand named after the building.

Word family

pentagonal adjective

having five sides

pentagram noun

a five-pointed star

hexagon noun

a shape with six sides

penta- prefix

a prefix meaning five

Commonly confused: pentagon or pentagon vs. pentagram? pentagon or hexagon?

Practice

Make it your own

Write a sentence using “pentagon”, then check it and compare it with the examples above.

Explore more words