In physical sciences, subatomic particles can be composite particles, such as the neutron and proton, or elementary particles. Based on the standard model, elementary particles are not made of other particles. Particle physics and nuclear physics study these particles and how they interact.

Subatomic particles are smaller than atoms. Experiments showed that light could behave like a stream of particles (called photons) as well as exhibiting wave-like properties. This led to the concept of wave–particle duality to reflect that quantum-scale particles behave like both particles and waves (they are sometimes described as waveicles to reflect this).

Another concept, the uncertainty principle, states that some of their properties taken together, such as their simultaneous position and momentum, cannot be measured exactly. The wave–particle duality has been shown to apply not only to photons but to more massive particles as well.

Interactions of particles in the framework of quantum field theory are understood as creation and annihilation of quanta of corresponding fundamental interactions. This blends particle physics with field theory.

Even among particle physicists, the exact definition of a particle has diverse descriptions. These professional attempts at the definition of a particle include:

 

Note:   The above text is excerpted from the Wikipedia article Subatomic particle, which has been released under the GNU Free Documentation License.