hydrogen

noun

hy·​dro·​gen ˈhī-drə-jən 

-dər-

: a nonmetallic gaseous chemical element with atomic number 1 that is the simplest and lightest of the elements and that is used especially in the processing of fossil fuels and the synthesis of ammonia

—often used before another noun

hydrogen gas

hydrogen atoms

a hydrogen vehicle

the hydrogen industry

see Chemical Elements Table compare deuterium, tritium

hydrogenous

hī-ˈdrä-jə-nəs 

adjective

Examples of hydrogen in a Sentence

Recent Examples on the Web

The team’s protonic ceramic electrochemical cell (PCEC) stores and generates electricity and produces hydrogen from water. —Aman Tripathi, Interesting Engineering, 4 Sep. 2025

The plan extends to other areas of focus for India’s maritime industry, including strengthening shipbuilding, ship recycling and ship repairs, and the launch of green hydrogen hubs and sustainable shipping solutions. —Glenn Taylor, Sourcing Journal, 4 Sep. 2025

In recent years, local transit agencies have increasingly adopted hydrogen fuel cell buses, and thousands of California drivers have bought personal hydrogen cars, though fuel availability has proved spotty. —Sacbee.com, 4 Sep. 2025

The 390-footer is the world’s first superyacht to be powered entirely by pure green hydrogen. —Michael Verdon, Robb Report, 3 Sep. 2025

Word History

Etymology

French hydrogène, from hydr- + -gène -gen; from the fact that water is generated by its combustion

First Known Use

1788, in the meaning defined above

Phrases Containing hydrogen

• heavy hydrogen
• hydrogen bomb
• hydrogen bond
• hydrogen bromide
• hydrogen chloride
• hydrogen cyanide
• hydrogen fluoride
• hydrogen iodide
• hydrogen ion
• hydrogen peroxide
• hydrogen sulfide

Rhymes for hydrogen

• dihydrogen

Kids Definition

hydrogen

noun

hy·​dro·​gen ˈhī-drə-jən 

: a chemical element that is the simplest and lightest of all chemical elements and is normally found alone as a colorless odorless highly flammable gas having two atoms per molecule see element

hydrogenous

hī-ˈdräj-ə-nəs 

adjective

Etymology

from French hydrogène "hydrogen," from hydr- "water" and -gène "producer"; so called because when hydrogen gas burns, it combines with oxygen to produce water

Medical Definition

hydrogen

noun

hy·​dro·​gen ˈhī-drə-jən 

: a nonmetallic element that is the simplest and lightest of the elements and that is normally a colorless odorless highly flammable diatomic gas

—symbol H see deuterium, tritium Chemical Elements Table

hydrogenous

hī-ˈdräj-ə-nəs 

adjective