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mercury
mercurynouna heavy, silver-white, highly toxic metallic element, the only one that is liquid at room temperature; quicksilver: used in barometers, thermometers, pesticides, pharmaceutical preparations, reflecting surfaces of mirrors, and dental fillings, in certain switches, lamps, and other electric apparatus, and as a laboratory catalyst. Hg; 200.59; 80; 13.546 at 20°C; freezing point: −38.9°C; boiling point: 357°C.
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Mercury
MercurynounRoman myth the messenger of the gods
mercury
Americannoun
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Chemistry. a heavy, silver-white, highly toxic metallic element, the only one that is liquid at room temperature; quicksilver: used in barometers, thermometers, pesticides, pharmaceutical preparations, reflecting surfaces of mirrors, and dental fillings, in certain switches, lamps, and other electric apparatus, and as a laboratory catalyst. Hg; 200.59; 80; 13.546 at 20°C; freezing point: −38.9°C; boiling point: 357°C.
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Pharmacology. this metal as used in medicine, in the form of various organic and inorganic compounds, usually for skin infections.
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(initial capital letter) the ancient Roman god who served as messenger of the gods and was also the god of commerce, thievery, eloquence, and science, identified with the Greek god Hermes.
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(initial capital letter) the planet nearest the sun, having a diameter of 3,031 miles (4,878 km), a mean distance from the sun of 36 million miles (57.9 million km), and a period of revolution of 87.96 days, and having no satellites: the smallest planet in the solar system.
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a messenger, especially a carrier of news.
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any plant belonging to the genus Mercurialis, of the spurge family, especially the poisonous, weedy M. perennis of Europe.
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(initial capital letter) one of a series of U.S. spacecraft, carrying one astronaut, that achieved the first U.S. suborbital and orbital manned spaceflights.
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Also called: quicksilver. hydrargyrum. a heavy silvery-white toxic liquid metallic element occurring principally in cinnabar: used in thermometers, barometers, mercury-vapour lamps, and dental amalgams. Symbol: Hg; atomic no: 80; atomic wt: 200.59; valency: 1 or 2; relative density: 13.546; melting pt: –38.842°C; boiling pt: 357°C
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any plant of the euphorbiaceous genus Mercurialis See dog's mercury
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archaic a messenger or courier
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The planet closest to the Sun and the smallest in the solar system. Mercury is a terrestrial or inner planet, second in density only to Earth, with a rugged, heavily-cratered surface similar in appearance to Earth's Moon. Its rotational period of 58.6 days is two-thirds of its 88-day orbital period, thus, it makes three full axial rotations every two years. Mercury's atmosphere is almost nonexistent; this fact, which produces rapid radiational cooling on its dark side, together with its proximity to the Sun, gives it a temperature range greater than any other planet in the solar system, from 466° to −184°C (870° to −300°F). Because it is so close to the Sun, Mercury is only visible shortly before sunrise or after sunset, and observation is further hindered by the fact that its light must pass obliquely through the lower atmosphere where it is distorted or filtered by dust and pollution.
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See Table at solar system
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A silvery-white, dense, poisonous metallic element that is a liquid at room temperature and is used in thermometers, barometers, batteries, and pesticides. Atomic number 80; atomic weight 200.59; melting point −38.87°C; boiling point 356.58°C; specific gravity 13.546 (at 20°C); valence 1, 2.
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See Periodic Table
Word History
Like a few other elements, mercury has a chemical symbol, Hg, that bears no resemblance to its name. This is because Hg is an abbreviation of the Latin name of the element, which was hydrargium. This word in turn was taken over from Greek, where it literally meant “water-silver.” With this name the Greeks were referring to the fact that mercury is a silvery liquid at room temperature, rather than a solid like other metals. Similarly, an older English name for this element is quicksilver, which means “living silver,” referring to its ability to move like a living thing. (The word quick used to mean “alive,” as in the Biblical phrase “the quick and the dead.”) The name mercury refers to the fact that the element flows about quickly: the name comes from the Roman god Mercury, who was the swift-footed messenger of the gods.
Discover More
The planet nearest the sun is named Mercury. It moves swiftly in its orbit like the messenger of the gods.
Mercury is sometimes visible from the Earth as a morning or evening star.
The term mercury is used figuratively in such expressions as “The mercury's rising” to mean that the temperature is going up.
Other Word Forms
Etymology
Origin of mercury
1300–50; Middle English Mercurie < Medieval Latin, Latin Mercurius, akin to merx goods
Explanation
Mercury is a silvery, liquid metal element. Before scientists understood how dangerous mercury is, several artists designed mercury fountains that were full of the strangely beautiful substance. Another common name for mercury is quicksilver, and if you've ever seen a blob of mercury rolling around, you'll understand why. This silver-colored element is the only metal that's liquid at room temperature, and old-style thermometers have mercury inside that rises and falls to indicate temperature. One of the most beautiful and fascinating elements, it's also incredibly toxic for humans. Mercury's name came from its association with the planet and the swift-moving Roman god it's named after.
Vocabulary lists containing mercury
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
BBC Newsbeat reporter Jimmy Blake described the absence as a "missed opportunity" at a breakthrough time from grime, with Stormzy headlining Glastonbury and Dave winning the Mercury Prize.
From BBC • Jun. 5, 2026
Intel remains the biggest supplier of CPUs for traditional Windows PCs, with a market share of about 64% in the final quarter of last year, according to Mercury Research.
From The Wall Street Journal • Jun. 2, 2026
Then, in February, the administration formalized the rollback of the Mercury and Air Toxics Standards, in effect making the exemptions permanent.
From Salon • May 10, 2026
The Mercury lost Sabally but still brought back five of their top six scorers from last season.
From Los Angeles Times • May 8, 2026
Although it had been too long in coming, the women of the Mercury 13 were still amazed that the day had finally arrived.
From "Women in Space" by Karen Bush Gibson
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Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.