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

Pretty early against Duke, the team seemed resolved to win with high-percentage throws to talented receivers on the perimeter working against slower defenders. Christopher Smith, al, "Betting: Alabama must solve running game against New Mexico State," 2 Sep. 2019 The fabric banners that decorate the perimeter fencing around the work zone will be rolled up and tied down, the spokeswoman said, so the wind can flow freely through the fencing. Matthew J. Palm, orlandosentinel.com, "Dr. Phillips Center crane will ride out Hurricane Dorian with the wind," 31 Aug. 2019 Some of the rooms in the Reach have glass walls and large, swinging doors that create a welcoming breach in the defensive perimeter. Philip Kennicott, Washington Post, "Does the Kennedy Center have a vision for its elegant but awkward new annex?," 30 Aug. 2019 Avdija is a capable set shooter, if not an overly dynamic one pulling up, but his perimeter skill set makes sense as a bigger guard in the modern NBA. Jeremy Woo, SI.com, "Summer Stock Watch: Where 2020 NBA Draft Prospects Stand," 29 Aug. 2019 But that is not the case at the moment at power forward, nor in the perimeter rotation. Ira Winderman, sun-sentinel.com, "ASK IRA: Does Heat commitment to Adebayo, Olynyk preclude small ball?," 27 Aug. 2019 Peterman can do things on the perimeter and moves the chains more gradually. Jerry Mcdonald, The Mercury News, "Raiders’ newest acquisition Corey Liuget: ‘I’m in rare form now’," 26 Aug. 2019 Deputies set up a perimeter and SWAT officers went door-to-door inside a sprawling building complex to search for the shooter. Houston Chronicle, "Authorities: Los Angeles deputy lied about sniper assault," 25 Aug. 2019 Only people with structures that lie within the boundaries of the current fire perimeter can receive the notifications. Anchorage Daily News, "Residents will be able to find out Friday whether their structures were destroyed in the McKinley fire," 23 Aug. 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

5 Sep 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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