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diameter

[dahy-am-i-ter]
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noun
  1. Geometry.
    1. a straight line passing through the center of a circle or sphere and meeting the circumference or surface at each end.
    2. a straight line passing from side to side of any figure or body, through its center.
  2. the length of such a line.
  3. the width of a circular or cylindrical object.
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Origin of diameter

1350–1400; Middle English diametre < Old French < Latin diametros < Greek diámetros diagonal, diameter, equivalent to dia- dia- + -metros, derivative of métron meter1
Can be confusedcircumference diameter radius tangent
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words

width, breadth, bore, caliber, broadness, module

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British Dictionary definitions for diameter

diameter

noun
    1. a straight line connecting the centre of a geometric figure, esp a circle or sphere, with two points on the perimeter or surface
    2. the length of such a line
  1. the thickness of something, esp with circular cross section
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Word Origin

C14: from Medieval Latin diametrus, variant of Latin diametros, from Greek: diameter, diagonal, from dia- + metron measure
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

Word Origin and History for diameter

n.

late 14c., from Old French diametre, from Latin diametrus, from Greek diametros (gramme) "diagonal of a circle," from dia- "across, through" (see dia-) + metron "a measure" (see meter (n.2)).

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Online Etymology Dictionary, © 2010 Douglas Harper

diameter in Medicine

diameter

(dī-ămĭ-tər)
n.
  1. A straight line connecting two opposite points on the surface of a spherical or cylindrical body, or at the boundary of an opening or foramen, passing through the center of such body or opening.
  2. The distance measured along such a line.
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

diameter in Science

diameter

[dī-ămĭ-tər]
  1. A straight line segment that passes through the center of a circle or sphere from one side to the other.
  2. The length of such a line segment.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

diameter in Culture

diameter

[(deye-am-uh-tuhr)]

A straight line passing through the center of a figure, especially a circle or sphere, and joining two opposite points on its circumference.

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The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.