diameter

noun di·am·e·ter \dī-ˈa-mə-tər\

: 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

: a chord passing through the center of a figure or body

: the length of a straight line through the center of an object

: 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>

— di·am·e·tral \-ˈa-mə-trəl\ adjective

See diameter defined for English-language learners

See diameter defined for kids

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

Other Mathematics and Statistics Terms

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

Rhymes with DIAMETER

decameter, heptameter, hexameter, octameter, parameter, pentameter, tetrameter

DIAMETRAL Defined for Kids

diameter

noun di·am·e·ter \dī-ˈa-mə-tər\

Definition of DIAMETER for Kids

: a straight line that runs from one side of a figure and passes through the center <Measure the diameter of the circle.>

: 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

noun di·am·e·ter \dī-ˈam-ət-ər\

Medical Definition of DIAMETER

: 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>

: one of the maximal breadths of a part of the body <the transverse diameter of the inlet of the pelvis>