diameter

noun di·am·e·ter \ dī-ˈa-mə-tər \

|Updated on: 19 Aug 2018

Examples: diameter in a Sentence

Definition of diameter

1 mathematics : a chord (see ³chord 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

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diametral

play \-ˈa-mə-trəl\ adjective

See diameter defined for English-language learners

See diameter defined for kids

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 of diameter from the Web

The nectar-producing plant makes a large dense mound (6 feet tall and 8 feet in diameter).

— calvin finch, San Antonio Express-News, "The plants that will attract fall hummingbirds, butterflies," 13 July 2018
For the lava bombs, our charges were made of something called detonating cord, a small-diameter cord filled with explosive powder.

— popular mechanics editors, Popular Mechanics, "The Secrets of Summer 2018's Greatest Movie Stunts and Effects," 20 June 2018
Also in Seattle: The new 2.5-mile State Route 99 tunnel, set to open to traffic this year, is the hemisphere’s largest-diameter bored tunnel.

— aarian marshall, WIRED, "This Week in the Future of Cars: The Big Dig," 17 June 2018
Divide the contents of the mixing bowl into two 5-inch-diameter ramekins.

— sally singer, Vogue, "Hollywood’s Favorite Detox Resort Launches a Delicious Vegetarian Cookbook," 13 June 2018
The Giant Magellan, by contrast, achieves its power by combining seven 8-meter-diameter mirrors.

— dennis overbye, New York Times, "Extremely Large, Extremely Expensive: The Race for the Next Giant Telescopes," 11 June 2018
High-performance Brembo brakes with large-diameter discs designed to dissipate heat quickly delivered short stopping distances.

— emma jayne williams, star-telegram, "Kia’s all-new 2018 Stinger sport sedan offers premium features, performance | Fort Worth Star-Telegram," 12 May 2018
That means that a new shade tree must be protected by 6-foot-tall, 6-foot-diameter fence around it until the crown grows out of reach, and the cork bark layer develops.

— calvin finch, San Antonio Express-News, "The deer-proof plants you should plant this spring," 11 May 2018
Annual Tithonia rotundifolia makes a single main stalk up to 6 feet tall, and with side branches, each of which sports 4-inch-diameter sunflowers in deep, intense orange.

— nan sterman, sandiegouniontribune.com, "April in the garden," 5 Apr. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'diameter.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of diameter

Middle English diametre, from Middle French, from Latin diametros, from Greek, from dia- + metron measure — more at measure

NEW! Time Traveler

First Known Use: 14th century

in the meaning defined at sense 1

See Words from the same year

Other Mathematics and Statistics Terms

abscissa, denominator, divisor, equilateral, exponent, hypotenuse, logarithm, oblique, radii, rhomb

DIAMETER Defined for English Language Learners

diameter

noun

Definition of diameter for English Language Learners

: a straight line from one side of something (such as a circle) to the other side that passes through the center point
: the distance through the center of something from one side to the other

DIAMETER Defined for Kids

diameter

noun di·am·e·ter \ dī-ˈa-mə-tər \

Definition of diameter for Students

1 : a straight line that runs from one side of a figure and passes through the center

Measure the diameter of the circle.

2 : the distance through the center of an object from one side to the other : thickness

the diameter of a tree trunk

Word Root of diameter

The Greek word metron, meaning “measure,” gives us the root metr. Words from the Greek metron have something to do with measuring. A thermometer is an instrument that measures temperature. A diameter is the measurement across the center of a circle. The metric system is a system used for measuring size, weight, and volume. A perimeter is the measurement of the outside of a figure or shape.