perimeter

noun

pe·​rim·​e·​ter pə-ˈri-mə-tər 

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.

Synonyms

• border
• borderline
• bound
• boundary
• brim
• circumference
• compass
• confines
• edge
• edging
• end
• frame
• fringe
• hem
• margin
• periphery
• rim
• skirt
• skirting
• verge

Examples of perimeter in a Sentence

He scored from the perimeter.

soldiers guarding the perimeter of the camp

Recent Examples on the Web

In a recent renovation, county officials added metal detectors in the lobby of the election center and additional fencing around its perimeter. —Sasha Hupka, The Arizona Republic, 31 Oct. 2024

For security reasons, this typically means the LLM needs to be within the security perimeter of the organization (either on-premise or through a VPN). —Mike Flaxman, Forbes, 21 Oct. 2024

The work at the organization's flagship building is expected to commence shortly after the construction company forms a perimeter around the work area at the Main Street building and take about 300 days to complete, said Christian Adelberg, spokesperson for Kentucky Performing Arts. —Killian Baarlaer, The Courier-Journal, 17 Oct. 2024

The 1981 quarantine perimeter spread like a gourmand’s belt size: 450 square miles in August, to 3,100 by September. —Patt Morrison, Los Angeles Times, 15 Oct. 2024

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

Phrases Containing perimeter

• the perimeter

Kids Definition

perimeter

noun

pe·​rim·​e·​ter pə-ˈrim-ət-ər 

: 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 

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