# perimeter

## noun

pe·​rim·​e·​ter
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.

## Examples of perimeter in a Sentence

He scored from the perimeter. soldiers guarding the perimeter of the camp
Recent Examples on the Web Meanwhile, another brush fire cropped up about 60 miles northwest of the Bridge fire Wednesday morning at the north perimeter of the Angeles National Forest in Palmdale. Hannah Fry, Los Angeles Times, 11 Sep. 2024 Organizations no longer operate within a specified boundary or perimeter. Steve Durbin, Forbes, 11 Sep. 2024 By reflecting on how documentary filmmakers approach these simple yet complex territorial perimeters, the program will invite the audiences and artists to engage in meaningful discussion and nurture critical awareness. Matthew Carey, Deadline, 11 Sep. 2024 Getting into the lane to create quality perimeter looks for Jackson and others will be an objective Tuesday. Aaron Heisen, Orange County Register, 9 Sep. 2024

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'perimeter.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

## 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

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

perimeter

## Cite this Entry

“Perimeter.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/perimeter. Accessed 20 Sep. 2024.

## Kids Definition

perimeter

noun
pe·​rim·​e·​ter
: the boundary of a shape or area
also : the length of such a boundary

## Medical Definition

perimeter

noun
pe·​rim·​e·​ter
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

## More from Merriam-Webster on perimeter

Last Updated: - Updated example sentences
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