mercury

noun

mer·​cu·​ry ˈmər-kyə-rē 

-k(ə-)rē

plural mercuries

1

a

Mercury : a Roman god of commerce, eloquence, travel, cunning, and theft who serves as messenger to the other gods compare hermes

b

often Mercury archaic : a bearer of messages or news or a conductor of travelers

2

[Middle English mercurie, from Medieval Latin mercurius, from Latin, the god]

a

: a silver-white poisonous heavy metallic element that is liquid at ordinary temperatures and is used especially in batteries, in dental amalgam, and in scientific instruments

called also quicksilver

see Chemical Elements Table

b

: the column of mercury in a thermometer or barometer

also : temperature

the mercury rose above 70 degrees

3

Mercury : the planet nearest the sun see Planets Table

Examples of mercury in a Sentence

In the summer, the mercury can reach over 100 degrees Fahrenheit.

Recent Examples on the Web

In San Bernardino and Riverside counties, temperatures are expected to linger in the mid- to high 90s with the mercury rising to 95 degrees in Lake Elsinore, 96 degrees in San Bernardino, 97 degrees in Palm Springs and 100 degrees in Thermal. —Hannah Fry, Los Angeles Times, 10 Mar. 2026

Hot, dry Santa Ana winds pushed the temperature to 89 degrees Sunday in San Diego, the highest recorded on March 8 since 1875 when the mercury rose to 85, the National Weather Service says. —Gary Robbins, San Diego Union-Tribune, 9 Mar. 2026

Because some types, such as king mackerel, are higher in mercury, opt for lower-mercury varieties such as Atlantic or Spanish mackerel when possible. —Morgan Pearson, Verywell Health, 9 Mar. 2026

Toxic materials, including mercury used to extract gold from ore, pour into rivers, contaminating the water and harming the workers, wildlife and surrounding communities that rely on local fish and wildfire. —Antonio MacHado Allison, The Conversation, 6 Mar. 2026

Word History

Etymology

Latin Mercurius, Roman god and the planet

First Known Use

14th century, in the meaning defined at sense 1a

Phrases Containing mercury

• bichloride of mercury
• mercury chloride
• mercury-vapor lamp

Rhymes for mercury

• methylmercury

Kids Definition

mercury

noun

mer·​cu·​ry ˈmər-kyə-rē 

-k(ə-)rē

1

a

: a heavy silver-white poisonous metallic element that is liquid at ordinary temperatures

called also quicksilver

see element

b

: the column of mercury in a formerly common type of thermometer or barometer

2

capitalized : the planet nearest the sun see planet

Medical Definition

mercury

noun

mer·​cu·​ry ˈmər-kyə-rē, -k(ə-)rē 

plural mercuries

1

: a heavy silver-white poisonous metallic element that is liquid at ordinary temperatures and used especially in scientific instruments

—symbol Hg

called also quicksilver

see Chemical Elements Table

2

: a pharmaceutical preparation containing mercury or a compound of it