diameter
noun
di·am·e·ter
dī-ˈa-mə-tər 
1
mathematics
: a chord (see chord entry 3 sense 2) passing through the center of a figure or body
2
mathematics
: the length of a straight line through the center of an object or space
the diameter of a circle
dug a hole nearly four feet in diameter
3
physics
: a unit of enlargement used with a number to indicate magnification by a lens or optical system
an object one millimeter wide magnified 40 diameters appears 40 millimeters wide
Examples of diameter in a Sentence
The dotted line indicates the diameter of the circle.
What is the diameter of the tree trunk?
Dig a hole that's two feet deep and three feet in diameter.
Recent Examples on the Web
This is a mid-sized 222 that measures 34mm in diameter, and most importantly, gets a two-toned case consisting of steel and yellow gold.
—
Allen Farmelo, Robb Report, 17 Jan. 2025
The round stainless steel case, measuring 39 mm in diameter and 9.25 mm in thickness, houses a mechanical self-winding movement, the RW4200, which boasts a power reserve of 41 hours.
—Bhanu Chopra, Forbes, 17 Jan. 2025
Blue Origin New Glenn is the size of a 30-story skyscraper at 322 feet tall, nearly as tall as the Saturn V rockets that carried the Apollo missions to the moon, and 23 feet in diameter.
—Michael Sheetz, CNBC, 16 Jan. 2025
His water cannon line is capable of delivering over 90 gallons a minute out 200 feet in diameter, according to his website.
—Stephanie Fuerte, NBC News, 16 Jan. 2025
See all Example Sentences for diameter 
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Allen Farmelo, Robb Report, 17 Jan. 2025
The round stainless steel case, measuring 39 mm in diameter and 9.25 mm in thickness, houses a mechanical self-winding movement, the RW4200, which boasts a power reserve of 41 hours.
—Bhanu Chopra, Forbes, 17 Jan. 2025
Blue Origin New Glenn is the size of a 30-story skyscraper at 322 feet tall, nearly as tall as the Saturn V rockets that carried the Apollo missions to the moon, and 23 feet in diameter.
—Michael Sheetz, CNBC, 16 Jan. 2025
His water cannon line is capable of delivering over 90 gallons a minute out 200 feet in diameter, according to his website.
—Stephanie Fuerte, NBC News, 16 Jan. 2025
See all Example Sentences for diameter
Dictionary Entries Near diameter
Cite this Entry
“Diameter.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/diameter. Accessed 22 Jan. 2025.
Copy CitationKids Definition
diameter
noun
di·am·e·ter
dī-ˈam-ət-ər
1
: a straight line passing through the center of a figure or body
especially
: a line segment through the center of a circle with its ends on the circle's circumference
2
: the length of a diameter
Medical Definition
diameter
noun
di·am·e·ter
dī-ˈam-ət-ər
1
: a unit of magnification for an optical instrument equal to the number of times the linear dimensions of an object are apparently increased
a microscope magnifying 60 diameters
2
: one of the maximal breadths of a part of the body
the transverse diameter of the inlet of the pelvis
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