Subatomic particles can vary in size. However, it's important to note that the concept of size becomes less straightforward when dealing with particles at the subatomic level because they do not possess well-defined boundaries like macroscopic objects.
Particles such as electrons, quarks, and neutrinos are considered point-like or elementary particles, which means they have no spatial extent or size in the classical sense. According to our current understanding, these particles are considered to be fundamental and indivisible.
On the other hand, composite particles, such as protons and neutrons, are made up of quarks held together by the strong nuclear force. These composite particles do have a size associated with them, typically measured in terms of their charge distribution. For example, the proton and neutron have a finite size with a radius of about 0.8 femtometers (10^−15 meters).
It's worth noting that the size of composite particles can be influenced by various factors, including the distribution of quarks within the particle and the cloud of virtual particles that surround it.
In summary, while elementary particles are often considered point-like with no size, composite particles can have a measurable size associated with them. However, it's essential to keep in mind that the concept of size becomes more subtle and less intuitive when dealing with subatomic particles compared to macroscopic objects.