diameter

noun di·am·e·ter \ dī-ˈa-mə-tər \

|Updated on: 10 Jun 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

If the storms become severe, the primary threat will be gusty to strong winds and small hail, although hail up to 1 inch in diameter is possible.

— robert a. cronkleton, kansascity, "Thunderstorms return Thursday in KC; here's what it means for the weekend," 6 June 2018
That puts the grain diameter at 0.2 to 0.3 millimeters—the size of an average sand grain on Earth.

— scott k. johnson, Ars Technica, "Frozen Pluto has wind-blown dunes made of methane sand," 31 May 2018
The diameter of the proto-planet would have been between 2,485 and 3,728 miles.

— ashley strickland, CNN, "These diamonds are from one of our solar system's 'lost planets'," 17 May 2018
Three black hoops are expected to encircle the diameter of the socks, while the initials of Los Blancos will adorn the front of the footwear in something of a departure for the club.

— SI.com, "PHOTO: Real Madrid 2018/19 Home Kit Leaks Online Ahead of Official Unveiling," 2 May 2018
Calculations like the diameter of the arena and the horse’s speed flashed through Villanueva’s mind, now a subconscious process after years of practice that began at age 7 in Guanajuato, Mexico.

— jasper scherer, San Antonio Express-News, "Charros and escaramuzas excite crowd at fan-favorite Fiesta Charreada," 30 Apr. 2018
Height And now, my last piece of good advice: Never make a sandwich whose height exceeds the diameter of your yawning maw.

— james p. dewan, chicagotribune.com, "Does your sandwich pass the eatability test?," 18 Apr. 2018
The largest diameter officially measured was three inches — surprisingly, not a record for the warmest state in the Lower 48.

— matthew cappucci, Washington Post, "Three-inch hail and multiple tornadoes raked the Sunshine State on Tuesday," 11 Apr. 2018
And ESA’s Characterizing Exoplanets Satellite (CHEOPS) will measure the diameters of alien planets whose masses are already known, allowing their approximate composition (rocky versus gaseous) to be deduced.

— mike wall, Scientific American, "European Space Agency Picks Exoplanet-Studying Spacecraft for 2028 Launch," 21 Mar. 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.