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

Inventory is stored on shelves that the robots, which resemble Roomba vacuum cleaners, pick up and deliver to people at workstations on the perimeter. Jennifer Smith, WSJ, "How Amazon Goes Small to Make It in New York," 1 Apr. 2019 When reconstituted, the achingly beautiful form became a roof, which was to be hoisted onto 10 wood columns staking out a simple rectangular perimeter. David Netto, Town & Country, "Frank Gehry Built a Tiny House for Michael Eisner," 19 Mar. 2019 The kids trotted along the new perimeter and set up small white marker flags, delineating for Millie the outline of what would soon be her confined space. C.j. Chivers, Popular Mechanics, "The Best Thing To Do When Your Dog Won't Stay," 24 Dec. 2018 The actual extent of his spying was scurrying around the perimeter suspiciously enough to get caught. Joshua Robinson, WSJ, "On His Manager’s Secret Service: Espionage Comes to English Soccer," 15 Jan. 2019 Yesterday's disruption at Heathrow has been minor compared to the holiday mess at Gatwick Airport, which shut down after an airport security officer spotted two drones flying over a perimeter road. David Hambling, Popular Mechanics, "What Are Airports Going to Do About Drones?," 9 Jan. 2019 In the Southwest, homes often have completely flat roofs with castle-like parapets lining the perimeter. Maggie Burch, House Beautiful, "What Is Spanish Colonial Design? Everything To Know About California's Popular Style," 13 Nov. 2018 One option is to use quartz only around the perimeter, with another material, like wood, on the kitchen island. Jessica Dailey, Good Housekeeping, "Countertops," 11 Feb. 2019 The tsunami left Taro looking like a bald man’s pate: surviving houses on the high-ground perimeter, total devastation on the low-lying plain. Jonathan Kolatch, WSJ, "Japan’s Tsunami Recovery Holds Lessons for the World," 8 Oct. 2018

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

18 Apr 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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Comments on perimeter

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