boson

In physics, an elementary particle whose spin can only take values that are whole numbers or zero. Bosons may be classified as gauge bosons (carriers of the four fundamental forces) or mesons. All elementary particles are either bosons or fermions.

Unlike fermions, more than one boson in a system (such as an atom) can possess the same energy state. That is, they do not obey the Pauli exclusion principle. When developed mathematically, this statement is known as the Bose-Einstein law, after its discoverers Indian physicist Satyendra Bose and Albert Einstein.