C1noun10K+

Hydrogen

UK /["/ˈhaɪdrədʒən/"]/US /["/ˈhaɪdrədʒən/"]/

Definition

a chemical element. Hydrogen is a gas that is the lightest of all the elements. It combines with oxygen to form water.

In simple words: A light gas that is a part of water and many other substances.

Examples

  • Hydrogen is the simplest element on the periodic table.
  • Many cars are now using hydrogen as a renewable fuel source.
  • The reaction of hydrogen and oxygen creates water.

Usage notes

Used in scientific contexts, often when discussing chemistry or energy. Can be informal when discussing hydrogen fuel or technologies but should not be used in casual conversation without context.

Grammar pattern

standalone noun

Memory hint

Think of 'high' energy – hydrogen is a fuel for energy.

Collocations

  • hydrogen gas
  • hydrogen bond
  • hydrogen fuel

Synonyms

  • fuel
  • element
  • gas

Common mistakes

  • Confused with 'hydroxide' (the ion) instead of hydrogen (the element).
  • Mispronounced as 'hydro-gen' instead of 'high-dro-jen'.