Hydrogen

/ˈhaɪdrəʤən/

Meaning & Definition

noun
A colorless, odorless, highly flammable gas that is the lightest and most abundant chemical element in the universe, represented by the symbol H and atomic number 1.
Hydrogen is used as a fuel in many rocket propulsion systems.
A chemical element that is a constituent of water and many organic compounds.
Water consists of two hydrogen atoms bonded to one oxygen atom.
A part of the molecular structure in many organic molecules, contributing to their chemical properties.
The hydrogen atoms in hydrocarbons play a critical role in their reactivity.
A gas that can be utilized for energy production and storage.
Hydrogen fuel cells are an emerging technology for clean energy generation.

Etymology

From the Greek word 'hydro' meaning water and 'genes' meaning creator or former.

Common Phrases and Expressions

hydrogen bond
A type of chemical bond that occurs when a hydrogen atom covalently bonded to a more electronegative atom is attracted to another electronegative atom.
hydrogen economy
An economic system that uses hydrogen as a key energy carrier.

Related Words

hydrogenation
The process of adding hydrogen to an organic compound.
hydroxide
A compound containing the hydroxyl ion, OH^-.

Slang Meanings

H2
When referring to hydrogen gas, people often just say H2.
Rocket fuel
In the context of space travel, hydrogen is sometimes called 'rocket fuel'.