molecule, atom, particle, speck, grain

1. A particle, such as an electron, a proton, or a neutron, having half-integral spin and obeying statistical rules requiring that not more than one in a set of identical particles may occupy a particular quantum state.
   費密子一種如電子、質子或中子等自旋為半整數的基本粒子，具有一種使得不可能有多于一個的粒子占有任何一個特殊的量子力學態(tài)的量子力學對稱性
2. There wasn't a particle of truth in what he said.
   他說的沒有一點真話。
3. We can see the dust particles floating in the sunlight clearly.
   我們可以很清楚地看到陽光下的灰塵顆粒。