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 Authorities established a perimeter and began searching the area for the suspects, State Police said. BostonGlobe.com, "One suspect is in custody as police in several communities search for others wanted in connection to car thefts and three separate crashes in Sharon and North Attleborough on Tuesday evening, State Police said.," 6 Nov. 2019 Officers then established a perimeter around the area and after 10 minutes Adams was arrested in the backyard of a residence near the 8100 block of Lisa Circle in Prescott Valley, according to police. Gabriella Khalaj, azcentral, "18-year-old arrested after pointing gun at people at Prescott Valley skate park," 30 Oct. 2019 Officers set up a perimeter around the area of the offense, but Bryant escaped. Madeline Mitchell, Cincinnati.com, "Man led traffic chase by 5 police departments throughout Greater Cincinnati after hit/skip, still at large," 24 Oct. 2019 Suttles said local officers, with help from the Pasadena Police Department, set up a perimeter to catch the men. Andy Nguyen, Glendale News-Press, "Glendale burglary suspects crash car in Pasadena while fleeing police," 22 Oct. 2019 As police began setting up a perimeter around a house in the 4100 block of Southeast 187th Place, a car left the home, giving off a tracking signal, police said. oregonlive, "Man arrested after stealing iPhones, Apple Watches in Vancouver armed robbery, police say," 18 Oct. 2019 Fire crews will focus on building a perimeter around the fire and use aircrafts to drop retardant on areas that are difficult to reach by land. San Diego Union-Tribune, "Firefighters make progress on Southern California wildfire," 13 Oct. 2019 Police set up a perimeter and officers, including a K-9, tried to track the suspects, but did not find them, Linders said. Mara H. Gottfried, Twin Cities, "Police: Suspect held gun to woman’s head in attempted robbery at St. Paul’s Lake Como," 8 Oct. 2019 Police set up a perimeter and used a drone to search for the suspect, but were unable to find him. Anna Bauman, SFChronicle.com, "Man attacks Menlo Park police officer in marsh during search for an ax-wielding suspect," 2 Oct. 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

14 Nov 2019

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
How to pronounce perimeter (audio)

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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