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

Green Tea May Lower Blood Pressure A normal blood pressure is less than 120/80 millimeters of mercury (mmHg). —Sarah Bence, Verywell Health, 20 Jan. 2026

Mercury in Aquarius encourages you to create space in your head. —Usa Today, USA Today, 20 Jan. 2026

Non-Rechargeable / Single Use Before 1996, single use batteries contained mercury and were therefore treated as hazardous waste, but the practice was phased out due to the Mercury-Containing and Rechargeable Battery Management Act. —Katherine Gallagher, Treehugger, 20 Jan. 2026

But the fun doesn’t end when the mercury rises; Pokagon and neighboring Trine State Recreation Area offer more than 10 miles of hiking trails as well as swimming, fishing, and boating at Lake James and Snow Lake. —Robert Annis, Midwest Living, 19 Jan. 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