bosons

• particles with integer spin (0, 1, 2, …), vs. fermions (half-integer)
• no Pauli exclusion: any number can share one quantum state (lasers, Bose-Einstein condensates)
• force carriers (spin 1): photon (electromagnetism), gluons (strong), W⁺, W⁻ and Z⁰ (weak)
• Higgs boson (spin 0): excitation of the Higgs field, which gives mass to the W and Z bosons, quarks and charged leptons
• hypothetical: graviton (spin 2), axions, majorons
• composite bosons contain an even number of fermions, e.g. mesons, helium-4 atoms (superfluid below 2.2 K)