Definition

1. Noun:
   • A plane figure with ten straight sides and ten angles: A decagon is a polygon that has exactly ten sides and ten interior angles. In a regular decagon, all sides are of equal length and all interior angles are equal (each measuring 144 degrees).

Usage Examples

• Noun:
  • The garden was designed in the shape of a perfect decagon.
  • A stop sign is an octagon, but if it had ten sides, it would be a decagon.
  • The students were asked to calculate the sum of the interior angles of a decagon.

Advanced Usage

• "Regular decagon": A decagon where all sides and all angles are equal.
  • The architect used a regular decagon as the floor plan for the pavilion.
• "Irregular decagon": A decagon where the sides and angles are not all equal.
  • The irregular decagon he drew had sides of varying lengths.

Variants and Related Words

• Decagonal (adj): Having the form of a decagon; related to a decagon.
  • The decagonal shape of the room was unusual.

Synonyms

• Ten-sided polygon: A direct descriptive synonym.
• 10-gon: A technical term used in geometry.

Related Terms (Conceptual)

• Polygon: The general category of plane figures with three or more straight sides, which includes triangles, quadrilaterals, pentagons, hexagons, and decagons.
• Perimeter: The total distance around the decagon.
• Interior angle: An angle inside the decagon formed by two adjacent sides.

Noun

1. a polygon with 10 sides and 10 angles