Which particle is NOT considered a fundamental subatomic particle?

In the context of subatomic particles, fundamental particles are those that are not made up of smaller components. Electrons, protons, and neutrons are commonly known particles, but there is a distinction in terms of their classification. Protons and neutrons, for example, are not fundamental because they are composed of quarks, which are considered fundamental particles.

On the other hand, electrons are fundamental particles themselves, as they do not have any substructure; they are part of the lepton family in the Standard Model of particle physics.

Nuclei, referring to the central cores of atoms, consist of protons and neutrons bound together and therefore are not fundamental either since they are made up of even smaller constituents.

The distinction becomes particularly clear with the choice that identifies nuclei. A nucleus is a composite structure formed from multiple protons and neutrons, establishing it as not fundamental in nature. Understanding this delineation helps clarify the classification of various particles in the realm of particle physics.