perimeter

noun

pe·​rim·​e·​ter pə-ˈri-mə-tər How to pronounce perimeter (audio)
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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Its perimeter defense was too inconsistent all night. Bennett Durando, The Denver Post, 5 Dec. 2024 Related Articles These Maryland football signees could make an instant impact in 2025 No. 7 Maryland women’s basketball improves to 9-0 with 87-52 win over Mount St. Mary’s Gillespie said perimeter defense was stressed as a key by the Maryland coaches. Edward Lee, Baltimore Sun, 5 Dec. 2024 Their brilliance frequently masked the lack of shooting or the spotty perimeter defense. Rohan Nadkarni, NBC News, 5 Dec. 2024 More often than not, companies today are oblivious to encryption as a data security tool and are content to use perimeter security measures like firewalls, monitoring and multifactor authentication to guard against would-be adversaries. Ameesh Divatia, Forbes, 4 Dec. 2024 See all Example Sentences for perimeter 

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

Dictionary Entries Near perimeter

Cite this Entry

“Perimeter.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/perimeter. Accessed 21 Dec. 2024.

Kids Definition

perimeter

noun
pe·​rim·​e·​ter pə-ˈrim-ət-ər How to pronounce perimeter (audio)
: the boundary of a shape or area
also : the length of such a boundary

Medical Definition

perimeter

noun
pe·​rim·​e·​ter pə-ˈrim-ət-ər How to pronounce perimeter (audio)
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
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!