A small unit or piece of matter; in science, often refers to atoms, molecules, or fine particles.
大気中の微粒子（PM2.5）の濃度が上がると健康に影響が出ることがある。
When the concentration of fine particles (PM2.5) in the atmosphere rises, it can affect health.
光は波であると同時に粒子でもあるという性質を示すのが光の粒子性だ。
The particle nature of light refers to the fact that light exhibits particle-like properties as well as wave-like ones.
砂糖は小さな粒子が集まってできている。
Sugar is made up of many small granules.