- The European Organization for Nuclear Research, a major laboratory located near Geneva on the Swiss-French border.
- An object which is sub-atomic - smaller than an atom - and has a definite mass and charge.
- A particle with mass, made up of smaller units called quarks that are bound together. Protons and electrons are types of hadron.
- CERN's Large Hadron Collider that has been under development for 20 years, with a total project cost of 10 billion Swiss francs ($9.4 billion).
- A machine used to accelerate streams of particles in a defined direction at high speeds. The LHC is the world's largest.
- An accelerator in which two beams traveling in opposite directions are steered together to induce high-energy collisions between particles in one beam and those in the other.
- A theoretical particle which is thought to give matter its mass. First proposed by Peter Higgs of the University of Edinburgh in 1964. The LHC should confirm whether it exists.
- The standard theory of modern physics, based on two other theories - general relativity and quantum mechanics. Its main weakness is that it cannot yet fully describe gravity or mass.
- The planets, stars and entire galaxies that give out light and can be seen from Earth - but which scientists say account for only 5 percent of everything in the universe.
- Invisible matter that scientists believe makes up some 25 percent of the universe and whose presumed existence accounts for how the trajectories through of visible stars and galaxies are bent.
- A mysterious, invisible material that has an anti-gravitational power believed to be powering the acceleration of the expansion of the universe, of which it makes up 70 percent.
