perimeter

American  

[puh-rim-i-ter] / pəˈrɪm ɪ tər /

noun

1. a line bounding or marking off an area.

   The police created a perimeter with caution tape around the crime scene.

2. the outermost limits.

   Under the new regulations, the smoke-free area for playgrounds and sports areas extends 20 meters from the perimeter of each site.

3. Geometry.

   1. the border or outer boundary of a two-dimensional figure.

   2. the length of such a boundary.

4. Military. a fortified boundary that protects a troop position.

5. Ophthalmology. an instrument for determining the peripheral field of vision.

6. Basketball. Often the perimeter

   1. Also called three-point line.  a semicircular line on a basketball court surrounding the basket, outside of which field goals are worth three points rather than two.

   2. the area outside this line (often used attributively).

      There's no player in the NBA who puts more pressure on opposing defenses from the perimeter than him.

      The team needs an efficient point guard with a great perimeter shot.

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perimeter British  

/ ˌpɛrɪˈmɛtrɪk, pəˈrɪmɪtə /

noun

1. maths

   1. the curve or line enclosing a plane area

   2. the length of this curve or line

2. 1. any boundary around something, such as a field

   2. ( as modifier )

      a perimeter fence

      a perimeter patrol

3. a medical instrument for measuring the limits of the field of vision

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perimeter Scientific  

/ pə-rĭm′ĭ-tər /

1. The sum of the lengths of the segments that form the sides of a polygon.

2. The total length of any closed curve, such as the circumference of a circle.

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Other Word Forms

Derived Forms

• perimeterless
  adjective
• perimetric
  adjective
• perimetrically
  adverb
• perimetrical
  adjective
• perimetry
  noun
• perimetral
  adjective

Etymology

Origin of perimeter

First recorded in 1585–95; from French périmètre, from Latin perimetros (feminine), from Greek perímetron (neuter); equivalent to peri- + -meter

Explanation

The noun perimeter refers to the border of an enclosed space. The perimeter of a house is its property line. For a country, it would be that country’s borders. From Latin peri meaning “around” and metron meaning “measure,” a perimeter is basically a boundary of any kind, measuring around the shape. In mathematics, perimeter refers to the length of this boundary. In geometry class, you might be asked to calculate the perimeter of a polygon, which is the sum of the length of each side. You might also hear this word used by members of the military or a police force as in “secure the perimeter” or “the perimeter has been breached.” A basketball player that likes to shoot from the three point line is said to “operate on the perimeter.”

Example Sentences

To solve this problem, Gurian and his co-author Simon May, a former Perimeter postdoctoral researcher now serving as an ERC Preparative Fellow at Bielefeld University, developed a new code called KISS-SIDM.

From Science Daily • Jan. 19, 2026

The flame retardant is a product called Phos-Chek, which is sold by a company called Perimeter.

From BBC • Jan. 13, 2025

Perimeter players finally sparked the offense as guard Kelsey Plum hit two three-pointers and assisted on a transition layup by Wilson during an 8-0 U.S. run.

From Los Angeles Times • Aug. 11, 2024

Broderick is a professor in the physics and astronomy department at Canada's University of Waterloo and an associate faculty at the Perimeter Institute.

From Salon • Mar. 28, 2024

So, what I'm trying to say is that there's an extremely badass carnival in the parking lot of Perimeter Mall today, and it's apparently open until nine.

From "Simon vs. the Homo Sapiens Agenda" by Becky Albertalli

Related Words

• boundary
• confines
• edge
• fringe
• periphery