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>
diametralplay \-ˈa-mə-trəl\ adjective
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
DIAMETER Defined for English Language Learners
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
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.
Medical 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>
Seen and Heard
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