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Definition of "diameter" []

  • Mathematics A straight line segment passing through the center of a figure, especially of a circle or sphere, and terminating at the periphery. (noun)
  • Mathematics The length of such a segment. (noun)
  • Thickness or width. (noun)
  • A unit for measuring the magnifying power of a microscope lens or telescope, equal to the number of times an object's linear dimensions are apparently increased. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Use "diameter" in a sentence
  • "Then, a line of tiny holes, less than one-millionth of a meter in diameter, is punched into the metal, spaced five micrometers apart."
  • "How many millimeters in diameter is the watch case?"
  • "Local lore has long maintained the tree, whose massive partially hollowed trunk measures 7 feet in diameter, is the very one featured in the biblical tale of Jesus and Zacchaeus, the tax collector of short stature who, according to the Gospel of Luke, climbed the tree to get a better look at Jesus."