perimeter

noun

pe·​rim·​e·​ter pə-ˈri-mə-tər 

1

a

: the boundary of a closed plane figure

b

: the length of a perimeter

2

: a line or strip bounding or protecting an area

3

: outer limits

—often used in plural

4

: the part of a basketball court outside the three-point line

Did you know?

Parameter vs. Perimeter

It's very easy to confuse parameter with perimeter. Not only do the two words sound the same, they both connote a boundary or limit.

When parameter is used to mean "a boundary or limit," it is usually in its plural form, and often as the object of a preposition such as within or beyond:

Let's face it, managing weight loss or maintenance can be trying enough within the parameters of a daily routine.
Geoff Kerr, Weight Watchers, November 1991

Though candor sometimes encourages Bruno to "stray beyond the parameters of good taste," his interaction with Lydia is always convincingly portrayed as a loving, tender relationship.
Ron Charles, The Washington Post, 8 Feb. 2011

In geometry, perimeter refers to the boundary of a closed plane figure. You might remember calculating perimeters in school. If each side of an equilateral triangle measures 9 feet, then the perimeter of the triangle measures 27 feet. In more general use, perimeter describes an outer stretch, as in "The college president lived in a house on the perimeter of the campus."

Parameter originally had a meaning pertaining to mathematics as well. The dictionary defines it as "an arbitrary constant whose value characterizes a member of a system (as a family of curves); also : a quantity (as a mean or variance) that describes a statistical population" as well as "an independent variable used to express the coordinates of a variable point and functions of them."

Some twentieth-century usage commentators objected to the use of a scientific-sounding word like parameter in general contexts (as in the examples above), especially to mean "a limit or boundary," theorizing that perimeter must have been what the speaker or writer intended.

However, perimeter was not often used in the phrasings that parameter is used in (that is, as the object of within or beyond) until much later. In fact, a word such as bounds or range or confines often serves as a more appropriate equivalent for parameter than the marginal connotations of perimeter:

But a true novel is an extended piece of fiction: Length is clearly one of its parameters.
Anthony Burgess, The New York Times Book Review, 5 Feb. 1984

Shields will then subsume that request in the overall City operating budget that he will recommend to the City Council in mid-March, and the Council will make its final decisions on the parameters of the budget, including any tax increases or cuts, by the end of April.
Nicholas F. Benton, The Falls Church News Press, 6 Jan. 2016

Did you know?

The perimeter of a prison is ringed with high walls and watchtowers, and the entire perimeter of Australia is bounded by water. In geometry, you may be asked to calculate the perimeter of various geometrical shapes. In basketball, the perimeter is the area beyond the free-throw circle; a "perimeter player" tends to stay outside that circle. Try not to confuse this word with parameter, which usually means a rule or limit that controls what something is or how it can be done.

Synonyms

• border
• borderline
• bound
• boundary
• brim
• circumference
• compass
• confines
• edge
• edging
• end
• frame
• fringe
• hem
• margin
• periphery
• rim
• skirt
• skirting
• verge

Examples of perimeter in a Sentence

He scored from the perimeter.

soldiers guarding the perimeter of the camp

Recent Examples on the Web

The chance of a deliberate burn escaping its perimeter — as happened last year in New Mexico’s largest fire in state history — remains a big challenge to the strategy. —Brian Melley, Fortune, 26 Oct. 2023

How Hamas attackers breached Israel's 'Iron Wall' As the world has seen, during the Oct. 7 incursion into Israel, Hamas did not rely on tunnels to breach the country’s security perimeter. —Ilan Ben Zion, Washington Post, 3 Nov. 2023

There was also work done to replace a mechanical equipment room and perimeter fence. —Tammy Murga, San Diego Union-Tribune, 1 Nov. 2023

The evacuation warning perimeter was also extended to west of the Cahuilla reservation boundary and north of the San Diego County line. —Jeremy Childs, Los Angeles Times, 31 Oct. 2023

An 11-piece band then led guests to the pool garden where drinks were served, while a Sicilian folklore band walked guests through the citrus garden, and finally everyone arrived at the courtyard where there was a table around its perimeter. —Alexandra MacOn, Vogue, 31 Oct. 2023

The Celtics receive a major boost in perimeter defense in Holiday. —Ryan Gaydos, Fox News, 1 Oct. 2023

Optimally, the visible perimeter of floor is no wider than 8 or 9 inches. —Michelle Slatalla, WSJ, 28 Sep. 2023

During the investigation, officers were set up on a perimeter around the scene. —Michael Williams, Dallas News, 14 Sep. 2023

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Word History

Etymology

Middle English perimetre, from Latin perimetros, from Greek, from peri- + metron measure — more at measure

First Known Use

15th century, in the meaning defined at sense 1a

Phrases Containing perimeter

• the perimeter

• the perimeter

Kids Definition

perimeter

noun

pe·​rim·​e·​ter pə-ˈrim-ət-ər 

: the boundary of a shape or area

also : the length of such a boundary

Medical Definition

perimeter

noun

pe·​rim·​e·​ter pə-ˈrim-ət-ər 

1

a

: the boundary of a closed plane figure

b

: the length of a perimeter

2

: an instrument for examining the discriminative powers of different parts of the retina often consisting of an adjustable semicircular arm with a fixation point for the eye and variable stations for the visual stimuli