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
If the branch is more than an inch in diameter, remove it in sections to reduce the weight.
—
Beth Botts, Chicago Tribune, 22 Feb. 2025
The giant snails, which can grow to 8 inches long with a 5-inch diameter shell, indiscriminately eat at least 500 different types of plants.
—Alan Clemons, Outdoor Life, 20 Feb. 2025
Many are made to increase the diameter of each strand, improving your hair’s overall density and volume.
—Malia Griggs, Glamour, 19 Feb. 2025
The lady from New York, their big thing was called white hot hot dogs — really unique, smaller, and a larger ring bologna diameter.
—Kristine M. Kierzek, Journal Sentinel, 15 Feb. 2025
See all Example Sentences for diameter 
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Beth Botts, Chicago Tribune, 22 Feb. 2025
The giant snails, which can grow to 8 inches long with a 5-inch diameter shell, indiscriminately eat at least 500 different types of plants.
—Alan Clemons, Outdoor Life, 20 Feb. 2025
Many are made to increase the diameter of each strand, improving your hair’s overall density and volume.
—Malia Griggs, Glamour, 19 Feb. 2025
The lady from New York, their big thing was called white hot hot dogs — really unique, smaller, and a larger ring bologna diameter.
—Kristine M. Kierzek, Journal Sentinel, 15 Feb. 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 25 Feb. 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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