A particle is a small quantity of matter with measureable properties, such as volume or density. In this sense, a particle can be a small amount of virtually any type of material. To be clear, however, the size of a particle can vary widely. While some particles are too small to be seen even on the microscopic level, others are large enough to be observable with only the naked eye. Particles on the smaller end of the size scale are among the fundamental building blocks of matter.

Salem Press Encyclopedia of Science, 2023. 2p.