Definition of diameter
1 mathematics : a chord (see ^{3}chord 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.
Origin and Etymology of diameter
Middle English diametre, from Medieval French, from Latin diametros, from Greek, from dia + metron measure — more at measure
First Known Use: 14th century
Other Mathematics and Statistics Terms
DIAMETER Defined for English Language Learners
diameter
playDefinition 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
playDefinition 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.
Medical Dictionary
diameter
playMedical Definition of diameter
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
Learn More about diameter

See words that rhyme with diameter Spanish Central: Translation of diameter Nglish: Translation of diameter for Spanish speakers Britannica English: Translation of diameter for Arabic speakers
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