perimeter

noun
pe·​rim·​e·​ter | \ pə-ˈri-mə-tər How to pronounce perimeter (audio) \

Definition of perimeter

1a : 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

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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.

Examples of perimeter in a Sentence

He scored from the perimeter. soldiers guarding the perimeter of the camp

Recent Examples on the Web

Some activists managed to march along the building’s perimeter, chanting and singing and banging on pots and pans with metal spoons, while others were turned away and told to keep to the sidewalk. Marissa J. Lang, Washington Post, "‘Quit your jobs’: Protesters confront ICE workers at Washington headquarters," 27 June 2018 Over time, the two probed the other’s perimeter, to relatively little effect. Adam Lashinsky, Fortune, "Alibaba v. Tencent: The Battle for Supremacy in China," 21 June 2018 While journalists have not been granted access to the facility, which is located about 40 miles southeast of El Paso, photographs have been taken from the air and from outside the facility’s perimeter. Diana Budds, Curbed, "This is the Texas tent camp meant as shelter for migrant children," 20 June 2018 According to the bill, private firms would be permitted to operate beyond their network’s perimeter in order to determine the source of an attack or to disrupt ongoing attacks. Rachel Aviv, The New Yorker, "The Digital Vigilantes Who Hack Back," 30 Apr. 2018 If the brightest fireflies converge near the center of the container, its glow will be most vivid there, even if a higher number of dimmer fireflies populate the container’s perimeter. Shannon Hall, Scientific American, "The Sun Is Spitting Out Strange Patterns of Gamma Rays—and No One Knows Why," 28 Mar. 2018 In Parkland, a walkout at Stoneman Douglas is expected to remain within the school’s perimeter, in part for safety reasons, Ashley Schulman, a 17-year-old senior, told the Wall Street Journal. Christopher Carbone, Fox News, "National School Walkout: Students protest gun violence, call for action one month after Parkland shooting," 14 Mar. 2018 Attacking the basket MSU’s perimeter players have been prone to settling for jump shots this season, particularly Bridges and Langford. Chris Solari, Detroit Free Press, "Michigan State basketball: 5 things to work on before NCAA tournament," 5 Mar. 2018 Ike Souzer escaped the Orange County Juvenile Hall, somehow got onto a roof and then jumped a perimeter fence just after midnight Friday, said Steve Sentman, chief probation officer for the county. Amanda Lee Myers, The Seattle Times, "Escaped teenager charged in mother’s death recaptured," 12 Apr. 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'perimeter.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of perimeter

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

History and Etymology for perimeter

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

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Statistics for perimeter

Last Updated

13 Jun 2019

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Time Traveler for perimeter

The first known use of perimeter was in the 15th century

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More Definitions for perimeter

perimeter

noun

English Language Learners Definition of perimeter

: the outside edge of an area or surface
: the total length of the lines that form a shape
basketball : the area on a basketball court that is not close to the basket

perimeter

noun
pe·​rim·​e·​ter | \ pə-ˈri-mə-tər How to pronounce perimeter (audio) \

Kids Definition of perimeter

1 : the whole outer boundary of a figure or area
2 : the length of the boundary of a figure

perimeter

noun
pe·​rim·​e·​ter | \ pə-ˈrim-ət-ər How to pronounce perimeter (audio) \

Medical Definition of perimeter

1a : 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

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