What is a particle?
A particle or a corpuscule in older texts is considered a small discrete portion of something that could be large, small, microscopic, or even smaller. A particle physicist will consider a neutron, proton, or electron as a particle or even smaller when looking at quarks or leptons. In physical sciences, a particle is a small, localized object which can be described by several physical or chemical properties, such as volume, density, or mass. In physics, a particle refers to its geometry with a specific shape within a range of dimensions.
The difference between particles is enormous in size, from extremely small electrons to nanoparticles to microns and, ultimately, to coarse powders. Macroscopically speaking, not all particles are solids. Water droplets in the air, oil droplets, and gas bubbles in the liquid also qualify as particles as well.
It is worth noting that the words “particulate” and “particulate matter (PM)” are terms used in environmental protection, which refer to particles suspended in the air.
Broadly speaking, when referring to size, particles can be described as macroscopic, microscopic, and subatomic. Macroscopic particles are the largest particles that can be seen by the naked eye. Microscopic particles are particles that are small enough to require at least a microscope to see them.