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

Downtown is currently tied for the most 100-degree-plus days in October with 1958 and 1971, but could surpass those years if the mercury hits 100 degrees Tuesday, according to the weather service. — Hannah Fry, Los Angeles Times, 5 Oct. 2026

Mercury in your partnership house squares Mars in your 4th, creating friction between another person’s perspective and what feels comfortable or settled to you. — Tarot.com, Hartford Courant, 2 Oct. 2026

Read the ingredient list carefully, however, as cat foods without fish in their name may still contain seafood ingredients and thus higher levels of mercury and cadmium. — Sandee Lamotte, CNN Money, 2 Oct. 2026

More than 1,000 harmful substances have been found in e-waste or produced when it is improperly recycled, including lead, mercury, cadmium and other toxic chemicals, according to the World Health Organization. — Aniruddha Ghosal, Chicago Tribune, 1 Oct. 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