Simple Definition of diameter
: 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
Full Definition of diameter
1 : a chord passing through the center of a figure or body
2 : the length of a straight line through the center of an object
3 : 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
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 of diameter
Middle English diametre, from Middle French, from Latin diametros, from Greek, from dia- + metron measure — more at measure
First Known Use: 14th century
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>
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