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[puh-rim-i-ter] /pəˈrɪm ɪ tər/
the border or outer boundary of a two-dimensional figure.
the length of such a boundary.
a line bounding or marking off an area.
the outermost limits.
Military. a fortified boundary that protects a troop position.
Ophthalmology. an instrument for determining the peripheral field of vision.
Origin of perimeter
1585-95; < French périmètre < Latin perimetros (feminine) < Greek perímetron (neuter). See peri-, -meter
Related forms
perimeterless, adjective
perimetral, perimetric
[per-uh-me-trik] /ˌpɛr əˈmɛ trɪk/ (Show IPA),
perimetrical, adjective
perimetrically, adverb
perimetry, noun
Can be confused
parameter, perimeter. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the Web for perimeter
Contemporary Examples
Historical Examples
  • But they were all in Government Center, marshaled there to try to hold a perimeter formed by bricked-up apartment buildings.

    The Hate Disease William Fitzgerald Jenkins
  • Also, the lowest part of the perimeter of a geometrical figure.

    The Sailor's Word-Book William Henry Smyth
  • Proclus remarked that the semicircle is the only plane figure that has its center on its perimeter.

    The Teaching of Geometry David Eugene Smith
  • The Radius is a right line drawne from the center to the perimeter.

    The Way To Geometry Peter Ramus
  • Ere night fell, Jai Singh and a sowar made an extensive reconnaissance on horseback beyond the perimeter of the village.

    The Great Mogul Louis Tracy
British Dictionary definitions for perimeter


  1. the curve or line enclosing a plane area
  2. the length of this curve or line
  1. any boundary around something, such as a field
  2. (as modifier): a perimeter fence, a perimeter patrol
a medical instrument for measuring the limits of the field of vision
Derived Forms
perimetric (ˌpɛrɪˈmɛtrɪk), perimetrical, adjective
perimetrically, adverb
perimetry, noun
Word Origin
C16: from French périmètre, from Latin perimetros; see peri-, -meter
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for perimeter

early 15c., "line around a figure or surface," from Latin perimetros, from Greek perimetron "circumference," from peri- "around" (see peri-) + metron "measure" (see meter (n.2)). Military sense of "boundary of a defended position" is attested from 1943.

Online Etymology Dictionary, © 2010 Douglas Harper
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perimeter in Medicine

perimeter pe·rim·e·ter (pə-rĭm'ĭ-tər)

  1. The outer limits of an area; circumference.

  2. An instrument used to measure field of vision.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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perimeter in Science
  1. The sum of the lengths of the segments that form the sides of a polygon.

  2. The total length of any closed curve, such as the circumference of a circle.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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